diff --git a/CMakeLists.txt b/CMakeLists.txt
index 30dfe42a30..23a6176a86 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -422,7 +422,6 @@ add_library(libopenmc SHARED
   src/xsdata.cpp)
 set_target_properties(libopenmc PROPERTIES
   OUTPUT_NAME openmc
-  PUBLIC_HEADER include/openmc.h
   LINKER_LANGUAGE Fortran)
 
 target_include_directories(libopenmc
@@ -492,8 +491,8 @@ install(TARGETS openmc libopenmc
   RUNTIME DESTINATION bin
   LIBRARY DESTINATION lib
   ARCHIVE DESTINATION lib
-  PUBLIC_HEADER DESTINATION include
   )
 install(DIRECTORY src/relaxng DESTINATION share/openmc)
 install(FILES man/man1/openmc.1 DESTINATION share/man/man1)
 install(FILES LICENSE DESTINATION "share/doc/openmc" RENAME copyright)
+install(DIRECTORY include/ DESTINATION include)
diff --git a/src/angle_energy.h b/include/openmc/angle_energy.h
similarity index 100%
rename from src/angle_energy.h
rename to include/openmc/angle_energy.h
diff --git a/include/openmc.h b/include/openmc/capi.h
similarity index 96%
rename from include/openmc.h
rename to include/openmc/capi.h
index b913d31b1a..8fd89334dc 100644
--- a/include/openmc.h
+++ b/include/openmc/capi.h
@@ -1,5 +1,5 @@
-#ifndef OPENMC_H
-#define OPENMC_H
+#ifndef OPENMC_CAPI_H
+#define OPENMC_CAPI_H
 
 #include <stdint.h>
 #include <stdbool.h>
@@ -37,7 +37,7 @@ extern "C" {
   int openmc_filter_set_id(int32_t index, int32_t id);
   int openmc_filter_set_type(int32_t index, const char* type);
   int openmc_finalize();
-  int openmc_find(double* xyz, int rtype, int32_t* id, int32_t* instance);
+  int openmc_find_cell(double* xyz, int32_t* index, int32_t* instance);
   int openmc_get_cell_index(int32_t id, int32_t* index);
   int openmc_get_filter_index(int32_t id, int32_t* index);
   void openmc_get_filter_next_id(int32_t* id);
@@ -166,14 +166,14 @@ extern "C" {
   extern int64_t openmc_work;
 
   // Run modes
-  constexpr int RUN_MODE_FIXEDSOURCE {1};
-  constexpr int RUN_MODE_EIGENVALUE {2};
-  constexpr int RUN_MODE_PLOTTING {3};
-  constexpr int RUN_MODE_PARTICLE {4};
-  constexpr int RUN_MODE_VOLUME {5};
+  const int RUN_MODE_FIXEDSOURCE = 1;
+  const int RUN_MODE_EIGENVALUE = 2;
+  const int RUN_MODE_PLOTTING = 3;
+  const int RUN_MODE_PARTICLE = 4;
+  const int RUN_MODE_VOLUME = 5;
 
 #ifdef __cplusplus
 }
 #endif
 
-#endif // OPENMC_H
+#endif // OPENMC_CAPI_H
diff --git a/src/cell.h b/include/openmc/cell.h
similarity index 99%
rename from src/cell.h
rename to include/openmc/cell.h
index 0b42a656c3..2b7534b582 100644
--- a/src/cell.h
+++ b/include/openmc/cell.h
@@ -10,7 +10,7 @@
 #include "hdf5.h"
 #include "pugixml.hpp"
 
-#include "position.h"
+#include "openmc/position.h"
 
 
 namespace openmc {
diff --git a/src/constants.h b/include/openmc/constants.h
similarity index 100%
rename from src/constants.h
rename to include/openmc/constants.h
diff --git a/src/distribution.h b/include/openmc/distribution.h
similarity index 99%
rename from src/distribution.h
rename to include/openmc/distribution.h
index 815248a2e6..ed71a1ee2a 100644
--- a/src/distribution.h
+++ b/include/openmc/distribution.h
@@ -10,7 +10,7 @@
 
 #include "pugixml.hpp"
 
-#include "constants.h"
+#include "openmc/constants.h"
 
 namespace openmc {
 
diff --git a/src/distribution_angle.h b/include/openmc/distribution_angle.h
similarity index 96%
rename from src/distribution_angle.h
rename to include/openmc/distribution_angle.h
index 1797e086a5..4344eb60db 100644
--- a/src/distribution_angle.h
+++ b/include/openmc/distribution_angle.h
@@ -6,9 +6,10 @@
 
 #include <vector> // for vector
 
-#include "distribution.h"
 #include "hdf5.h"
 
+#include "openmc/distribution.h"
+
 namespace openmc {
 
 //==============================================================================
diff --git a/src/distribution_energy.h b/include/openmc/distribution_energy.h
similarity index 99%
rename from src/distribution_energy.h
rename to include/openmc/distribution_energy.h
index 8dc4baffe4..f13bd5de45 100644
--- a/src/distribution_energy.h
+++ b/include/openmc/distribution_energy.h
@@ -9,8 +9,8 @@
 #include "xtensor/xtensor.hpp"
 #include "hdf5.h"
 
-#include "constants.h"
-#include "endf.h"
+#include "openmc/constants.h"
+#include "openmc/endf.h"
 
 namespace openmc {
 
diff --git a/src/distribution_multi.h b/include/openmc/distribution_multi.h
similarity index 97%
rename from src/distribution_multi.h
rename to include/openmc/distribution_multi.h
index 2d4dab42c1..c93f22d7bc 100644
--- a/src/distribution_multi.h
+++ b/include/openmc/distribution_multi.h
@@ -3,8 +3,8 @@
 
 #include <memory>
 
-#include "distribution.h"
-#include "position.h"
+#include "openmc/distribution.h"
+#include "openmc/position.h"
 
 namespace openmc {
 
diff --git a/src/distribution_spatial.h b/include/openmc/distribution_spatial.h
similarity index 97%
rename from src/distribution_spatial.h
rename to include/openmc/distribution_spatial.h
index 7474b497ca..bda4e8cf0e 100644
--- a/src/distribution_spatial.h
+++ b/include/openmc/distribution_spatial.h
@@ -3,8 +3,8 @@
 
 #include "pugixml.hpp"
 
-#include "distribution.h"
-#include "position.h"
+#include "openmc/distribution.h"
+#include "openmc/position.h"
 
 namespace openmc {
 
diff --git a/src/endf.h b/include/openmc/endf.h
similarity index 98%
rename from src/endf.h
rename to include/openmc/endf.h
index 369f5d5a61..7f224b24fb 100644
--- a/src/endf.h
+++ b/include/openmc/endf.h
@@ -6,9 +6,10 @@
 
 #include <vector>
 
-#include "constants.h"
 #include "hdf5.h"
 
+#include "openmc/constants.h"
+
 namespace openmc {
 
 //! Convert integer representing interpolation law to enum
diff --git a/src/error.h b/include/openmc/error.h
similarity index 94%
rename from src/error.h
rename to include/openmc/error.h
index 7d015d6143..17b2f392ed 100644
--- a/src/error.h
+++ b/include/openmc/error.h
@@ -1,11 +1,11 @@
-#ifndef ERROR_H
-#define ERROR_H
+#ifndef OPENMC_ERROR_H
+#define OPENMC_ERROR_H
 
 #include <cstring>
 #include <string>
 #include <sstream>
 
-#include "openmc.h"
+#include "openmc/capi.h"
 
 namespace openmc {
 
@@ -82,4 +82,4 @@ void write_message(const std::stringstream& message, int level)
 }
 
 } // namespace openmc
-#endif // ERROR_H
+#endif // OPENMC_ERROR_H
diff --git a/include/openmc/finalize.h b/include/openmc/finalize.h
new file mode 100644
index 0000000000..58cf75606d
--- /dev/null
+++ b/include/openmc/finalize.h
@@ -0,0 +1,6 @@
+#ifndef OPENMC_FINALIZE_H
+#define OPENMC_FINALIZE_H
+
+extern "C" void openmc_free_bank();
+
+#endif // OPENMC_FINALIZE_H
diff --git a/src/geometry.h b/include/openmc/geometry.h
similarity index 100%
rename from src/geometry.h
rename to include/openmc/geometry.h
diff --git a/src/geometry_aux.h b/include/openmc/geometry_aux.h
similarity index 98%
rename from src/geometry_aux.h
rename to include/openmc/geometry_aux.h
index fb5940d1c9..a99cadc902 100644
--- a/src/geometry_aux.h
+++ b/include/openmc/geometry_aux.h
@@ -1,8 +1,8 @@
 //! \file geometry_aux.h
 //! Auxilary functions for geometry initialization and general data handling.
 
-#ifndef GEOMETRY_AUX_H
-#define GEOMETRY_AUX_H
+#ifndef OPENMC_GEOMETRY_AUX_H
+#define OPENMC_GEOMETRY_AUX_H
 
 #include <cstdint>
 
@@ -109,4 +109,4 @@ extern "C" int maximum_levels(int32_t univ);
 extern "C" void free_memory_geometry_c();
 
 } // namespace openmc
-#endif // GEOMETRY_AUX_H
+#endif // OPENMC_GEOMETRY_AUX_H
diff --git a/src/hdf5_interface.h b/include/openmc/hdf5_interface.h
similarity index 99%
rename from src/hdf5_interface.h
rename to include/openmc/hdf5_interface.h
index 6ef9a1895c..0191d4ffb5 100644
--- a/src/hdf5_interface.h
+++ b/include/openmc/hdf5_interface.h
@@ -13,7 +13,7 @@
 #include "xtensor/xadapt.hpp"
 #include "xtensor/xarray.hpp"
 
-#include "position.h"
+#include "openmc/position.h"
 
 namespace openmc {
 
diff --git a/src/initialize.h b/include/openmc/initialize.h
similarity index 74%
rename from src/initialize.h
rename to include/openmc/initialize.h
index 14283fb5fc..72ccc12f68 100644
--- a/src/initialize.h
+++ b/include/openmc/initialize.h
@@ -1,5 +1,5 @@
-#ifndef INITIALIZE_H
-#define INITIALIZE_H
+#ifndef OPENMC_INITIALIZE_H
+#define OPENMC_INITIALIZE_H
 
 #ifdef OPENMC_MPI
 #include "mpi.h"
@@ -17,4 +17,4 @@ void initialize_mpi(MPI_Comm intracomm);
 
 }
 
-#endif // INITIALIZE_H
+#endif // OPENMC_INITIALIZE_H
diff --git a/src/lattice.h b/include/openmc/lattice.h
similarity index 99%
rename from src/lattice.h
rename to include/openmc/lattice.h
index 94d7b43878..47544938d4 100644
--- a/src/lattice.h
+++ b/include/openmc/lattice.h
@@ -10,8 +10,8 @@
 #include "hdf5.h"
 #include "pugixml.hpp"
 
-#include "constants.h"
-#include "position.h"
+#include "openmc/constants.h"
+#include "openmc/position.h"
 
 
 namespace openmc {
diff --git a/src/material.h b/include/openmc/material.h
similarity index 100%
rename from src/material.h
rename to include/openmc/material.h
diff --git a/src/math_functions.h b/include/openmc/math_functions.h
similarity index 98%
rename from src/math_functions.h
rename to include/openmc/math_functions.h
index 4df1a9240a..a3c9c07cf0 100644
--- a/src/math_functions.h
+++ b/include/openmc/math_functions.h
@@ -7,9 +7,9 @@
 #include <cmath>
 #include <cstdlib>
 
-#include "constants.h"
-#include "position.h"
-#include "random_lcg.h"
+#include "openmc/constants.h"
+#include "openmc/position.h"
+#include "openmc/random_lcg.h"
 
 
 namespace openmc {
@@ -93,8 +93,8 @@ extern "C" void calc_rn_c(int n, const double uvw[3], double rn[]);
 extern "C" void calc_zn_c(int n, double rho, double phi, double zn[]);
 
 //==============================================================================
-//! Calculate only the even radial components of n-th order modified Zernike 
-//! polynomial moment with azimuthal dependency m = 0 for a given angle 
+//! Calculate only the even radial components of n-th order modified Zernike
+//! polynomial moment with azimuthal dependency m = 0 for a given angle
 //! (rho, theta) location on the unit disk.
 //!
 //! Since m = 0, n could only be even orders. Z_q0 = R_q0
diff --git a/src/message_passing.h b/include/openmc/message_passing.h
similarity index 70%
rename from src/message_passing.h
rename to include/openmc/message_passing.h
index 14cf3a7cb0..1dab43139b 100644
--- a/src/message_passing.h
+++ b/include/openmc/message_passing.h
@@ -1,5 +1,5 @@
-#ifndef MESSAGE_PASSING_H
-#define MESSAGE_PASSING_H
+#ifndef OPENMC_MESSAGE_PASSING_H
+#define OPENMC_MESSAGE_PASSING_H
 
 #ifdef OPENMC_MPI
 #include "mpi.h"
@@ -19,4 +19,4 @@ namespace mpi {
 } // namespace mpi
 } // namespace openmc
 
-#endif // MESSAGE_PASSING_H
+#endif // OPENMC_MESSAGE_PASSING_H
diff --git a/src/mgxs.h b/include/openmc/mgxs.h
similarity index 98%
rename from src/mgxs.h
rename to include/openmc/mgxs.h
index 0434bd55d5..40746c291d 100644
--- a/src/mgxs.h
+++ b/include/openmc/mgxs.h
@@ -1,15 +1,15 @@
 //! \file mgxs.h
 //! A collection of classes for Multi-Group Cross Section data
 
-#ifndef MGXS_H
-#define MGXS_H
+#ifndef OPENMC_MGXS_H
+#define OPENMC_MGXS_H
 
 #include <string>
 #include <vector>
 
-#include "constants.h"
-#include "hdf5_interface.h"
-#include "xsdata.h"
+#include "openmc/constants.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/xsdata.h"
 
 
 namespace openmc {
@@ -202,4 +202,4 @@ class Mgxs {
 };
 
 } // namespace openmc
-#endif // MGXS_H
\ No newline at end of file
+#endif // OPENMC_MGXS_H
diff --git a/src/mgxs_interface.h b/include/openmc/mgxs_interface.h
similarity index 96%
rename from src/mgxs_interface.h
rename to include/openmc/mgxs_interface.h
index 65afd20f9c..e5f56e9975 100644
--- a/src/mgxs_interface.h
+++ b/include/openmc/mgxs_interface.h
@@ -1,8 +1,8 @@
 //! \file mgxs_interface.h
 //! A collection of C interfaces to the C++ Mgxs class
 
-#ifndef MGXS_INTERFACE_H
-#define MGXS_INTERFACE_H
+#ifndef OPENMC_MGXS_INTERFACE_H
+#define OPENMC_MGXS_INTERFACE_H
 
 #include "hdf5_interface.h"
 #include "mgxs.h"
@@ -76,4 +76,4 @@ extern "C" double
 get_awr_c(int index);
 
 } // namespace openmc
-#endif // MGXS_INTERFACE_H
\ No newline at end of file
+#endif // OPENMC_MGXS_INTERFACE_H
diff --git a/src/nuclide.h b/include/openmc/nuclide.h
similarity index 98%
rename from src/nuclide.h
rename to include/openmc/nuclide.h
index 8c43d55a0b..60769139f7 100644
--- a/src/nuclide.h
+++ b/include/openmc/nuclide.h
@@ -1,7 +1,7 @@
 #ifndef OPENMC_NUCLIDE_H
 #define OPENMC_NUCLIDE_H
 
-#include "constants.h"
+#include "openmc/constants.h"
 
 namespace openmc {
 
diff --git a/src/particle.h b/include/openmc/particle.h
similarity index 99%
rename from src/particle.h
rename to include/openmc/particle.h
index b533971710..f351d11866 100644
--- a/src/particle.h
+++ b/include/openmc/particle.h
@@ -7,7 +7,7 @@
 #include <cstdint>
 #include <array>
 
-#include "openmc.h"
+#include "openmc/capi.h"
 
 namespace openmc {
 
diff --git a/src/plot.h b/include/openmc/plot.h
similarity index 85%
rename from src/plot.h
rename to include/openmc/plot.h
index 75406b9ace..2048189f79 100644
--- a/src/plot.h
+++ b/include/openmc/plot.h
@@ -1,5 +1,5 @@
-#ifndef PLOT_H
-#define PLOT_H
+#ifndef OPENMC_PLOT_H
+#define OPENMC_PLOT_H
 
 #include "hdf5.h"
 
@@ -12,4 +12,4 @@ extern "C" void voxel_write_slice(int x, hid_t dspace, hid_t dset,
 extern "C" void voxel_finalize(hid_t dspace, hid_t dset, hid_t memspace);
 
 } // namespace openmc
-#endif // PLOT_H
+#endif // OPENMC_PLOT_H
diff --git a/src/position.h b/include/openmc/position.h
similarity index 100%
rename from src/position.h
rename to include/openmc/position.h
diff --git a/src/random_lcg.h b/include/openmc/random_lcg.h
similarity index 97%
rename from src/random_lcg.h
rename to include/openmc/random_lcg.h
index 45f6ba2c08..b02deec2c5 100644
--- a/src/random_lcg.h
+++ b/include/openmc/random_lcg.h
@@ -1,5 +1,5 @@
-#ifndef RANDOM_LCG_H
-#define RANDOM_LCG_H
+#ifndef OPENMC_RANDOM_LCG_H
+#define OPENMC_RANDOM_LCG_H
 
 #include <cstdint>
 
@@ -93,4 +93,4 @@ extern "C" int64_t openmc_get_seed();
 extern "C" void openmc_set_seed(int64_t new_seed);
 
 } // namespace openmc
-#endif // RANDOM_LCG_H
+#endif // OPENMC_RANDOM_LCG_H
diff --git a/src/reaction.h b/include/openmc/reaction.h
similarity index 98%
rename from src/reaction.h
rename to include/openmc/reaction.h
index 5efda042ad..7b4d32a94d 100644
--- a/src/reaction.h
+++ b/include/openmc/reaction.h
@@ -7,7 +7,8 @@
 #include <vector>
 
 #include "hdf5.h"
-#include "reaction_product.h"
+
+#include "openmc/reaction_product.h"
 
 namespace openmc {
 
diff --git a/src/reaction_product.h b/include/openmc/reaction_product.h
similarity index 95%
rename from src/reaction_product.h
rename to include/openmc/reaction_product.h
index ee8b5cea5f..79a22d2609 100644
--- a/src/reaction_product.h
+++ b/include/openmc/reaction_product.h
@@ -8,9 +8,10 @@
 #include <vector> // for vector
 
 #include "hdf5.h"
-#include "angle_energy.h"
-#include "endf.h"
-#include "particle.h"
+
+#include "openmc/angle_energy.h"
+#include "openmc/endf.h"
+#include "openmc/particle.h"
 
 namespace openmc {
 
diff --git a/src/scattdata.h b/include/openmc/scattdata.h
similarity index 98%
rename from src/scattdata.h
rename to include/openmc/scattdata.h
index efa7accb41..980238aeb5 100644
--- a/src/scattdata.h
+++ b/include/openmc/scattdata.h
@@ -1,11 +1,13 @@
 //! \file scattdata.h
 //! A collection of multi-group scattering data classes
 
-#ifndef SCATTDATA_H
-#define SCATTDATA_H
+#ifndef OPENMC_SCATTDATA_H
+#define OPENMC_SCATTDATA_H
 
 #include <vector>
 
+#include "openmc/constants.h"
+
 namespace openmc {
 
 // forward declarations so we can name our friend functions
@@ -257,4 +259,4 @@ convert_legendre_to_tabular(ScattDataLegendre& leg, ScattDataTabular& tab,
                             int n_mu);
 
 } // namespace openmc
-#endif // SCATTDATA_H
\ No newline at end of file
+#endif // OPENMC_SCATTDATA_H
diff --git a/src/search.h b/include/openmc/search.h
similarity index 100%
rename from src/search.h
rename to include/openmc/search.h
diff --git a/src/secondary_correlated.h b/include/openmc/secondary_correlated.h
similarity index 95%
rename from src/secondary_correlated.h
rename to include/openmc/secondary_correlated.h
index 1e3eab0ab5..8ba18d3d15 100644
--- a/src/secondary_correlated.h
+++ b/include/openmc/secondary_correlated.h
@@ -8,9 +8,10 @@
 
 #include "hdf5.h"
 #include "xtensor/xtensor.hpp"
-#include "angle_energy.h"
-#include "endf.h"
-#include "distribution.h"
+
+#include "openmc/angle_energy.h"
+#include "openmc/endf.h"
+#include "openmc/distribution.h"
 
 namespace openmc {
 
diff --git a/src/secondary_kalbach.h b/include/openmc/secondary_kalbach.h
similarity index 95%
rename from src/secondary_kalbach.h
rename to include/openmc/secondary_kalbach.h
index fa4c43694a..a898db67c8 100644
--- a/src/secondary_kalbach.h
+++ b/include/openmc/secondary_kalbach.h
@@ -8,9 +8,10 @@
 
 #include "hdf5.h"
 #include "xtensor/xtensor.hpp"
-#include "angle_energy.h"
-#include "constants.h"
-#include "endf.h"
+
+#include "openmc/angle_energy.h"
+#include "openmc/constants.h"
+#include "openmc/endf.h"
 
 namespace openmc {
 
diff --git a/src/secondary_nbody.h b/include/openmc/secondary_nbody.h
similarity index 97%
rename from src/secondary_nbody.h
rename to include/openmc/secondary_nbody.h
index f80d50670a..8509b07143 100644
--- a/src/secondary_nbody.h
+++ b/include/openmc/secondary_nbody.h
@@ -6,7 +6,7 @@
 
 #include "hdf5.h"
 
-#include "angle_energy.h"
+#include "openmc/angle_energy.h"
 
 namespace openmc {
 
diff --git a/src/secondary_uncorrelated.h b/include/openmc/secondary_uncorrelated.h
similarity index 92%
rename from src/secondary_uncorrelated.h
rename to include/openmc/secondary_uncorrelated.h
index 7f067fc0af..e895a17bdc 100644
--- a/src/secondary_uncorrelated.h
+++ b/include/openmc/secondary_uncorrelated.h
@@ -8,9 +8,10 @@
 #include <vector>
 
 #include "hdf5.h"
-#include "angle_energy.h"
-#include "distribution_angle.h"
-#include "distribution_energy.h"
+
+#include "openmc/angle_energy.h"
+#include "openmc/distribution_angle.h"
+#include "openmc/distribution_energy.h"
 
 namespace openmc {
 
diff --git a/src/settings.h b/include/openmc/settings.h
similarity index 100%
rename from src/settings.h
rename to include/openmc/settings.h
diff --git a/src/simulation.h b/include/openmc/simulation.h
similarity index 72%
rename from src/simulation.h
rename to include/openmc/simulation.h
index b7544a6da3..14bb56f27b 100644
--- a/src/simulation.h
+++ b/include/openmc/simulation.h
@@ -1,5 +1,5 @@
-#ifndef SIMULATION_H
-#define SIMULATION_H
+#ifndef OPENMC_SIMULATION_H
+#define OPENMC_SIMULATION_H
 
 #include <cstdint>
 
@@ -10,4 +10,4 @@ extern "C" int openmc_n_lost_particles;
 
 #pragma omp threadprivate(openmc_current_work)
 
-#endif // SIMULATION_H
+#endif // OPENMC_SIMULATION_H
diff --git a/src/state_point.h b/include/openmc/state_point.h
similarity index 74%
rename from src/state_point.h
rename to include/openmc/state_point.h
index 459df1a675..64713ae961 100644
--- a/src/state_point.h
+++ b/include/openmc/state_point.h
@@ -1,10 +1,11 @@
-#ifndef STATE_POINT_H
-#define STATE_POINT_H
+#ifndef OPENMC_STATE_POINT_H
+#define OPENMC_STATE_POINT_H
 
 #include <cstdint>
 
 #include "hdf5.h"
-#include "openmc.h"
+
+#include "openmc/capi.h"
 
 namespace openmc {
 
@@ -14,4 +15,4 @@ extern "C" void read_source_bank(hid_t group_id, int64_t* work_index,
                                  Bank* source_bank);
 
 } // namespace openmc
-#endif // STATE_POINT_H
+#endif // OPENMC_STATE_POINT_H
diff --git a/src/string_functions.h b/include/openmc/string_functions.h
similarity index 80%
rename from src/string_functions.h
rename to include/openmc/string_functions.h
index bf30612fe8..a3da179a06 100644
--- a/src/string_functions.h
+++ b/include/openmc/string_functions.h
@@ -1,8 +1,8 @@
 //! \file string_functions.h
 //! A collection of helper routines for C-strings and STL strings
 
-#ifndef STRING_FUNCTIONS_H
-#define STRING_FUNCTIONS_H
+#ifndef OPENMC_STRING_FUNCTIONS_H
+#define OPENMC_STRING_FUNCTIONS_H
 
 #include <string>
 
diff --git a/src/string_utils.h b/include/openmc/string_utils.h
similarity index 100%
rename from src/string_utils.h
rename to include/openmc/string_utils.h
diff --git a/src/surface.h b/include/openmc/surface.h
similarity index 99%
rename from src/surface.h
rename to include/openmc/surface.h
index 746db5c3b5..1c38118304 100644
--- a/src/surface.h
+++ b/include/openmc/surface.h
@@ -9,8 +9,8 @@
 #include "hdf5.h"
 #include "pugixml.hpp"
 
-#include "constants.h"
-#include "position.h"
+#include "openmc/constants.h"
+#include "openmc/position.h"
 
 
 namespace openmc {
diff --git a/src/thermal.h b/include/openmc/thermal.h
similarity index 97%
rename from src/thermal.h
rename to include/openmc/thermal.h
index e3571a0d56..265831e10e 100644
--- a/src/thermal.h
+++ b/include/openmc/thermal.h
@@ -1,5 +1,5 @@
-#ifndef OPENMC_THERMAL_SCATTERING_H
-#define OPENMC_THERMAL_SCATTERING_H
+#ifndef OPENMC_THERMAL_H
+#define OPENMC_THERMAL_H
 
 #include <cstddef>
 #include <string>
@@ -7,8 +7,8 @@
 
 #include "xtensor/xtensor.hpp"
 
-#include "hdf5_interface.h"
-#include "nuclide.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/nuclide.h"
 
 namespace openmc {
 
@@ -144,4 +144,4 @@ extern "C" {
 
 } // namespace openmc
 
-#endif // OPENMC_THERMAL_SCATTERING_H
+#endif // OPENMC_THERMAL_H
diff --git a/src/xml_interface.h b/include/openmc/xml_interface.h
similarity index 90%
rename from src/xml_interface.h
rename to include/openmc/xml_interface.h
index ec789cd4e2..fb87ffdae1 100644
--- a/src/xml_interface.h
+++ b/include/openmc/xml_interface.h
@@ -1,5 +1,5 @@
-#ifndef XML_INTERFACE_H
-#define XML_INTERFACE_H
+#ifndef OPENMC_XML_INTERFACE_H
+#define OPENMC_XML_INTERFACE_H
 
 #include <sstream> // for stringstream
 #include <string>
@@ -39,4 +39,4 @@ std::vector<T> get_node_array(pugi::xml_node node, const char* name,
 }
 
 } // namespace openmc
-#endif // XML_INTERFACE_H
+#endif // OPENMC_XML_INTERFACE_H
diff --git a/src/xsdata.h b/include/openmc/xsdata.h
similarity index 96%
rename from src/xsdata.h
rename to include/openmc/xsdata.h
index c855c67d89..156708c786 100644
--- a/src/xsdata.h
+++ b/include/openmc/xsdata.h
@@ -1,14 +1,14 @@
 //! \file xsdata.h
 //! A collection of classes for containing the Multi-Group Cross Section data
 
-#ifndef XSDATA_H
-#define XSDATA_H
+#ifndef OPENMC_XSDATA_H
+#define OPENMC_XSDATA_H
 
 #include <memory>
 #include <vector>
 
-#include "hdf5_interface.h"
-#include "scattdata.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/scattdata.h"
 
 
 namespace openmc {
@@ -115,4 +115,4 @@ class XsData {
 
 
 } //namespace openmc
-#endif // XSDATA_H
\ No newline at end of file
+#endif // OPENMC_XSDATA_H
diff --git a/openmc/capi/core.py b/openmc/capi/core.py
index b5ada7956b..f0c5ac45e4 100644
--- a/openmc/capi/core.py
+++ b/openmc/capi/core.py
@@ -24,10 +24,10 @@ _dll.openmc_calculate_volumes.restype = c_int
 _dll.openmc_calculate_volumes.errcheck = _error_handler
 _dll.openmc_finalize.restype = c_int
 _dll.openmc_finalize.errcheck = _error_handler
-_dll.openmc_find.argtypes = [POINTER(c_double*3), c_int, POINTER(c_int32),
-                             POINTER(c_int32)]
-_dll.openmc_find.restype = c_int
-_dll.openmc_find.errcheck = _error_handler
+_dll.openmc_find_cell.argtypes = [POINTER(c_double*3), POINTER(c_int32),
+                                  POINTER(c_int32)]
+_dll.openmc_find_cell.restype = c_int
+_dll.openmc_find_cell.errcheck = _error_handler
 _dll.openmc_hard_reset.restype = c_int
 _dll.openmc_hard_reset.errcheck = _error_handler
 _dll.openmc_init.argtypes = [c_int, POINTER(POINTER(c_char)), c_void_p]
@@ -84,10 +84,10 @@ def find_cell(xyz):
         indicates which instance it is, i.e., 0 would be the first instance.
 
     """
-    uid = c_int32()
+    index = c_int32()
     instance = c_int32()
-    _dll.openmc_find((c_double*3)(*xyz), 1, uid, instance)
-    return openmc.capi.cells[uid.value], instance.value
+    _dll.openmc_find_cell((c_double*3)(*xyz), index, instance)
+    return openmc.capi.Cell(index=index.value), instance.value
 
 
 def find_material(xyz):
@@ -104,11 +104,15 @@ def find_material(xyz):
         Material containing the point, or None is no material is found
 
     """
-    uid = c_int32()
+    index = c_int32()
     instance = c_int32()
-    _dll.openmc_find((c_double*3)(*xyz), 2, uid, instance)
-    return openmc.capi.materials[uid.value] if uid != 0 else None
+    _dll.openmc_find_cell((c_double*3)(*xyz), index, instance)
 
+    mats = openmc.capi.Cell(index=index.value).fill
+    if isinstance(mats, openmc.capi.Material):
+        return mats
+    else:
+        return mats[instance]
 
 def hard_reset():
     """Reset tallies, timers, and pseudo-random number generator state."""
diff --git a/src/api.F90 b/src/api.F90
index 51cc14766c..76be2f4460 100644
--- a/src/api.F90
+++ b/src/api.F90
@@ -51,7 +51,7 @@ module openmc_api
   public :: openmc_filter_set_id
   public :: openmc_filter_set_type
   public :: openmc_finalize
-  public :: openmc_find
+  public :: openmc_find_cell
   public :: openmc_get_cell_index
   public :: openmc_get_keff
   public :: openmc_get_filter_index
@@ -188,13 +188,12 @@ contains
   end function openmc_finalize
 
 !===============================================================================
-! OPENMC_FIND determines the ID or a cell or material at a given point in space
+! OPENMC_FIND_CELL determines what cell contains a given point in space
 !===============================================================================
 
-  function openmc_find(xyz, rtype, id, instance) result(err) bind(C)
+  function openmc_find_cell(xyz, index, instance) result(err) bind(C)
     real(C_DOUBLE), intent(in)        :: xyz(3) ! Cartesian point
-    integer(C_INT), intent(in), value :: rtype  ! 1 for cell, 2 for material
-    integer(C_INT32_T), intent(out)   :: id
+    integer(C_INT32_T), intent(out)   :: index
     integer(C_INT32_T), intent(out)   :: instance
     integer(C_INT) :: err
 
@@ -206,30 +205,22 @@ contains
     p % coord(1) % uvw(:) = [ZERO, ZERO, ONE]
     call find_cell(p, found)
 
-    id = -1
+    index = -1
     instance = -1
     err = E_UNASSIGNED
 
     if (found) then
-      if (rtype == 1) then
-        id = cells(p % coord(p % n_coord) % cell) % id()
-      elseif (rtype == 2) then
-        if (p % material == MATERIAL_VOID) then
-          id = 0
-        else
-          id = materials(p % material) % id()
-        end if
-      end if
+      index = p % coord(p % n_coord) % cell
       instance = p % cell_instance - 1
       err = 0
     else
       err = E_GEOMETRY
-      call set_errmsg("Could not find cell/material at position (" // &
+      call set_errmsg("Could not find cell at position (" // &
            trim(to_str(xyz(1))) // "," // trim(to_str(xyz(2))) // "," // &
            trim(to_str(xyz(3))) // ").")
     end if
 
-  end function openmc_find
+  end function openmc_find_cell
 
 !===============================================================================
 ! OPENMC_HARD_RESET reset tallies and timers as well as the pseudorandom
diff --git a/src/cell.cpp b/src/cell.cpp
index fb364cfdfb..f172ddf3b4 100644
--- a/src/cell.cpp
+++ b/src/cell.cpp
@@ -1,17 +1,17 @@
-#include "cell.h"
+#include "openmc/cell.h"
 
 #include <cmath>
 #include <sstream>
 #include <string>
 
-#include "constants.h"
-#include "error.h"
-#include "hdf5_interface.h"
-#include "lattice.h"
-#include "material.h"
-#include "openmc.h"
-#include "surface.h"
-#include "xml_interface.h"
+#include "openmc/capi.h"
+#include "openmc/constants.h"
+#include "openmc/error.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/lattice.h"
+#include "openmc/material.h"
+#include "openmc/surface.h"
+#include "openmc/xml_interface.h"
 
 
 namespace openmc {
diff --git a/src/distribution.cpp b/src/distribution.cpp
index f513701fb0..f02ee1fc09 100644
--- a/src/distribution.cpp
+++ b/src/distribution.cpp
@@ -1,4 +1,4 @@
-#include "distribution.h"
+#include "openmc/distribution.h"
 
 #include <algorithm> // for copy
 #include <cmath>     // for sqrt, floor, max
@@ -6,10 +6,10 @@
 #include <numeric>   // for accumulate
 #include <string>    // for string, stod
 
-#include "error.h"
-#include "math_functions.h"
-#include "random_lcg.h"
-#include "xml_interface.h"
+#include "openmc/error.h"
+#include "openmc/math_functions.h"
+#include "openmc/random_lcg.h"
+#include "openmc/xml_interface.h"
 
 namespace openmc {
 
diff --git a/src/distribution_angle.cpp b/src/distribution_angle.cpp
index e5263e4ac2..615f84f68a 100644
--- a/src/distribution_angle.cpp
+++ b/src/distribution_angle.cpp
@@ -1,15 +1,16 @@
-#include "distribution_angle.h"
+#include "openmc/distribution_angle.h"
 
 #include <cmath>  // for abs, copysign
 #include <vector> // for vector
 
-#include "endf.h"
-#include "hdf5_interface.h"
-#include "random_lcg.h"
-#include "search.h"
 #include "xtensor/xarray.hpp"
 #include "xtensor/xview.hpp"
 
+#include "openmc/endf.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/random_lcg.h"
+#include "openmc/search.h"
+
 namespace openmc {
 
 //==============================================================================
diff --git a/src/distribution_energy.cpp b/src/distribution_energy.cpp
index cadeeb3df1..d5a47957bb 100644
--- a/src/distribution_energy.cpp
+++ b/src/distribution_energy.cpp
@@ -1,16 +1,17 @@
-#include "distribution_energy.h"
+#include "openmc/distribution_energy.h"
 
 #include <algorithm> // for max, min, copy, move
 #include <cstddef>   // for size_t
 #include <iterator>  // for back_inserter
 
-#include "endf.h"
-#include "hdf5_interface.h"
-#include "math_functions.h"
-#include "random_lcg.h"
-#include "search.h"
 #include "xtensor/xview.hpp"
 
+#include "openmc/endf.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/math_functions.h"
+#include "openmc/random_lcg.h"
+#include "openmc/search.h"
+
 namespace openmc {
 
 //==============================================================================
diff --git a/src/distribution_multi.cpp b/src/distribution_multi.cpp
index 36184f7527..20ee074a81 100644
--- a/src/distribution_multi.cpp
+++ b/src/distribution_multi.cpp
@@ -1,11 +1,11 @@
-#include "distribution_multi.h"
+#include "openmc/distribution_multi.h"
 
 #include <algorithm> // for move
 #include <cmath>     // for sqrt, sin, cos, max
 
-#include "constants.h"
-#include "math_functions.h"
-#include "random_lcg.h"
+#include "openmc/constants.h"
+#include "openmc/math_functions.h"
+#include "openmc/random_lcg.h"
 
 namespace openmc {
 
diff --git a/src/distribution_spatial.cpp b/src/distribution_spatial.cpp
index d870a5f93a..ad61861e54 100644
--- a/src/distribution_spatial.cpp
+++ b/src/distribution_spatial.cpp
@@ -1,8 +1,8 @@
-#include "distribution_spatial.h"
+#include "openmc/distribution_spatial.h"
 
-#include "error.h"
-#include "random_lcg.h"
-#include "xml_interface.h"
+#include "openmc/error.h"
+#include "openmc/random_lcg.h"
+#include "openmc/xml_interface.h"
 
 namespace openmc {
 
diff --git a/src/endf.cpp b/src/endf.cpp
index 8a63893a79..fb7701ac3e 100644
--- a/src/endf.cpp
+++ b/src/endf.cpp
@@ -1,15 +1,16 @@
-#include "endf.h"
+#include "openmc/endf.h"
 
 #include <algorithm> // for copy
 #include <cmath>     // for log, exp
 #include <iterator>  // for back_inserter
 
-#include "constants.h"
-#include "hdf5_interface.h"
-#include "search.h"
 #include "xtensor/xarray.hpp"
 #include "xtensor/xview.hpp"
 
+#include "openmc/constants.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/search.h"
+
 namespace openmc {
 
 //==============================================================================
diff --git a/src/finalize.cpp b/src/finalize.cpp
index 696a1e80e5..3b4f26764c 100644
--- a/src/finalize.cpp
+++ b/src/finalize.cpp
@@ -1,6 +1,6 @@
-#include "finalize.h"
+#include "openmc/finalize.h"
 
-#include "message_passing.h"
+#include "openmc/message_passing.h"
 
 void openmc_free_bank()
 {
diff --git a/src/finalize.h b/src/finalize.h
deleted file mode 100644
index e606493ca1..0000000000
--- a/src/finalize.h
+++ /dev/null
@@ -1,6 +0,0 @@
-#ifndef FINALIZE_H
-#define FINALIZE_H
-
-extern "C" void openmc_free_bank();
-
-#endif // FINALIZE_H
diff --git a/src/geometry_aux.cpp b/src/geometry_aux.cpp
index b202620715..1f2b1e6777 100644
--- a/src/geometry_aux.cpp
+++ b/src/geometry_aux.cpp
@@ -1,14 +1,14 @@
-#include "geometry_aux.h"
+#include "openmc/geometry_aux.h"
 
 #include <algorithm>  // for std::max
 #include <sstream>
 #include <unordered_set>
 
-#include "cell.h"
-#include "constants.h"
-#include "error.h"
-#include "lattice.h"
-#include "material.h"
+#include "openmc/cell.h"
+#include "openmc/constants.h"
+#include "openmc/error.h"
+#include "openmc/lattice.h"
+#include "openmc/material.h"
 
 
 namespace openmc {
diff --git a/src/hdf5_interface.cpp b/src/hdf5_interface.cpp
index 74d26a58b6..cc82307398 100644
--- a/src/hdf5_interface.cpp
+++ b/src/hdf5_interface.cpp
@@ -1,4 +1,4 @@
-#include "hdf5_interface.h"
+#include "openmc/hdf5_interface.h"
 
 #include <array>
 #include <cstring>
@@ -9,9 +9,9 @@
 #include "hdf5_hl.h"
 #ifdef OPENMC_MPI
 #include "mpi.h"
-#include "message_passing.h"
+#include "openmc/message_passing.h"
 #endif
-#include "error.h"
+#include "openmc/error.h"
 
 
 namespace openmc {
diff --git a/src/initialize.cpp b/src/initialize.cpp
index 62eeea4099..59e13512ec 100644
--- a/src/initialize.cpp
+++ b/src/initialize.cpp
@@ -1,4 +1,4 @@
-#include "initialize.h"
+#include "openmc/initialize.h"
 
 #include <cstddef>
 #include <cstring>
@@ -6,15 +6,16 @@
 #include <sstream>
 #include <string>
 
-#include "error.h"
-#include "hdf5_interface.h"
-#include "message_passing.h"
-#include "openmc.h"
-#include "settings.h"
 #ifdef _OPENMP
 #include "omp.h"
 #endif
 
+#include "openmc/capi.h"
+#include "openmc/error.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/message_passing.h"
+#include "openmc/settings.h"
+
 // data/functions from Fortran side
 extern "C" void print_usage();
 extern "C" void print_version();
diff --git a/src/lattice.cpp b/src/lattice.cpp
index e2871d9e1a..a5b56eef8e 100644
--- a/src/lattice.cpp
+++ b/src/lattice.cpp
@@ -1,15 +1,15 @@
-#include "lattice.h"
+#include "openmc/lattice.h"
 
 #include <cmath>
 #include <sstream>
 #include <vector>
 
-#include "cell.h"
-#include "error.h"
-#include "geometry_aux.h"
-#include "hdf5_interface.h"
-#include "string_utils.h"
-#include "xml_interface.h"
+#include "openmc/cell.h"
+#include "openmc/error.h"
+#include "openmc/geometry_aux.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/string_utils.h"
+#include "openmc/xml_interface.h"
 
 
 namespace openmc {
diff --git a/src/main.cpp b/src/main.cpp
index 8d8f39e249..54b78d38d0 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -1,8 +1,8 @@
-#include "error.h"
 #ifdef OPENMC_MPI
 #include "mpi.h"
 #endif
-#include "openmc.h"
+#include "openmc/capi.h"
+#include "openmc/error.h"
 
 
 int main(int argc, char* argv[]) {
diff --git a/src/material.cpp b/src/material.cpp
index 409908e673..ec930f2082 100644
--- a/src/material.cpp
+++ b/src/material.cpp
@@ -1,10 +1,10 @@
-#include "material.h"
+#include "openmc/material.h"
 
 #include <string>
 #include <sstream>
 
-#include "error.h"
-#include "xml_interface.h"
+#include "openmc/error.h"
+#include "openmc/xml_interface.h"
 
 
 namespace openmc {
diff --git a/src/math_functions.cpp b/src/math_functions.cpp
index f2a5e415dd..5c1a2f4dce 100644
--- a/src/math_functions.cpp
+++ b/src/math_functions.cpp
@@ -1,4 +1,4 @@
-#include "math_functions.h"
+#include "openmc/math_functions.h"
 
 namespace openmc {
 
@@ -608,7 +608,7 @@ void calc_zn_rad_c(int n, double rho, double zn_rad[]) {
       double k2 = 2 * p * (p - 1) * (p - 2);
       double k3 = -q * q * (p - 1) - p * (p - 1) * (p - 2);
       double k4 = (-p * (p + q - 2) * (p - q - 2)) / 2.;
-      zn_rad[index] = 
+      zn_rad[index] =
         ((k2 * rho * rho + k3) * zn_rad[index-1] + k4 * zn_rad[index-2]) / k1;
     }
   }
diff --git a/src/message_passing.cpp b/src/message_passing.cpp
index 2ff3952d73..aac677c6ef 100644
--- a/src/message_passing.cpp
+++ b/src/message_passing.cpp
@@ -1,4 +1,4 @@
-#include "message_passing.h"
+#include "openmc/message_passing.h"
 
 namespace openmc {
 namespace mpi {
diff --git a/src/mgxs.cpp b/src/mgxs.cpp
index 3e84f63072..eb13a55f61 100644
--- a/src/mgxs.cpp
+++ b/src/mgxs.cpp
@@ -1,17 +1,18 @@
+#include "openmc/mgxs.h"
+
 #include <cmath>
 #include <cstdlib>
 #include <algorithm>
 #include <valarray>
 
- #ifdef _OPENMP
- # include <omp.h>
- #endif
+#ifdef _OPENMP
+#include <omp.h>
+#endif
 
-#include "error.h"
-#include "math_functions.h"
-#include "random_lcg.h"
-#include "string_functions.h"
-#include "mgxs.h"
+#include "openmc/error.h"
+#include "openmc/math_functions.h"
+#include "openmc/random_lcg.h"
+#include "openmc/string_functions.h"
 
 
 namespace openmc {
@@ -709,4 +710,4 @@ Mgxs::set_angle_index(const double uvw[3])
   }
 }
 
-} // namespace openmc
\ No newline at end of file
+} // namespace openmc
diff --git a/src/mgxs_interface.cpp b/src/mgxs_interface.cpp
index d875987791..f601f3c71e 100644
--- a/src/mgxs_interface.cpp
+++ b/src/mgxs_interface.cpp
@@ -1,8 +1,9 @@
+#include "openmc/mgxs_interface.h"
+
 #include <string>
 
-#include "error.h"
-#include "math_functions.h"
-#include "mgxs_interface.h"
+#include "openmc/error.h"
+#include "openmc/math_functions.h"
 
 
 namespace openmc {
@@ -226,4 +227,4 @@ get_awr_c(int index)
   return nuclides_MG[index - 1].awr;
 }
 
-} // namespace openmc
\ No newline at end of file
+} // namespace openmc
diff --git a/src/particle.cpp b/src/particle.cpp
index e46d06c011..51331cea03 100644
--- a/src/particle.cpp
+++ b/src/particle.cpp
@@ -1,14 +1,14 @@
-#include "particle.h"
+#include "openmc/particle.h"
 
 #include <algorithm>
 #include <sstream>
 
-#include "constants.h"
-#include "error.h"
-#include "hdf5_interface.h"
-#include "openmc.h"
-#include "settings.h"
-#include "simulation.h"
+#include "openmc/capi.h"
+#include "openmc/constants.h"
+#include "openmc/error.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/settings.h"
+#include "openmc/simulation.h"
 
 namespace openmc {
 
diff --git a/src/plot.cpp b/src/plot.cpp
index 0dca6d08cd..79f04c47f3 100644
--- a/src/plot.cpp
+++ b/src/plot.cpp
@@ -1,4 +1,4 @@
-#include "plot.h"
+#include "openmc/plot.h"
 
 namespace openmc {
 
diff --git a/src/position.cpp b/src/position.cpp
index 85e511041e..18ec33e803 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -1,4 +1,4 @@
-#include "position.h"
+#include "openmc/position.h"
 
 namespace openmc {
 
diff --git a/src/random_lcg.cpp b/src/random_lcg.cpp
index d82738ca1b..cf5d7e34bd 100644
--- a/src/random_lcg.cpp
+++ b/src/random_lcg.cpp
@@ -1,4 +1,5 @@
-#include "random_lcg.h"
+#include "openmc/random_lcg.h"
+
 #include <cmath>
 
 
diff --git a/src/reaction.cpp b/src/reaction.cpp
index 10e07b18aa..48eca15e08 100644
--- a/src/reaction.cpp
+++ b/src/reaction.cpp
@@ -1,12 +1,12 @@
-#include "reaction.h"
+#include "openmc/reaction.h"
 
 #include <string>
 #include <utility> // for move
 
-#include "hdf5_interface.h"
-#include "endf.h"
-#include "random_lcg.h"
-#include "secondary_uncorrelated.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/endf.h"
+#include "openmc/random_lcg.h"
+#include "openmc/secondary_uncorrelated.h"
 
 namespace openmc {
 
diff --git a/src/reaction_product.cpp b/src/reaction_product.cpp
index ef5c746bde..7e31753433 100644
--- a/src/reaction_product.cpp
+++ b/src/reaction_product.cpp
@@ -1,14 +1,14 @@
-#include "reaction_product.h"
+#include "openmc/reaction_product.h"
 
 #include <memory> // for unique_ptr
 #include <string> // for string
 
-#include "hdf5_interface.h"
-#include "random_lcg.h"
-#include "secondary_correlated.h"
-#include "secondary_kalbach.h"
-#include "secondary_nbody.h"
-#include "secondary_uncorrelated.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/random_lcg.h"
+#include "openmc/secondary_correlated.h"
+#include "openmc/secondary_kalbach.h"
+#include "openmc/secondary_nbody.h"
+#include "openmc/secondary_uncorrelated.h"
 
 namespace openmc {
 
diff --git a/src/scattdata.cpp b/src/scattdata.cpp
index a316eba46d..3e18c168f2 100644
--- a/src/scattdata.cpp
+++ b/src/scattdata.cpp
@@ -1,12 +1,13 @@
+#include "openmc/scattdata.h"
+
 #include <algorithm>
 #include <numeric>
 #include <cmath>
 
-#include "constants.h"
-#include "math_functions.h"
-#include "random_lcg.h"
-#include "error.h"
-#include "scattdata.h"
+#include "openmc/constants.h"
+#include "openmc/error.h"
+#include "openmc/math_functions.h"
+#include "openmc/random_lcg.h"
 
 namespace openmc {
 
diff --git a/src/secondary_correlated.cpp b/src/secondary_correlated.cpp
index b1653f3170..1acaf6551c 100644
--- a/src/secondary_correlated.cpp
+++ b/src/secondary_correlated.cpp
@@ -1,16 +1,17 @@
-#include "secondary_correlated.h"
+#include "openmc/secondary_correlated.h"
 
 #include <algorithm> // for copy
 #include <cmath>
 #include <cstddef>   // for size_t
 #include <iterator>  // for back_inserter
 
-#include "hdf5_interface.h"
 #include "xtensor/xarray.hpp"
 #include "xtensor/xview.hpp"
-#include "endf.h"
-#include "random_lcg.h"
-#include "search.h"
+
+#include "openmc/hdf5_interface.h"
+#include "openmc/endf.h"
+#include "openmc/random_lcg.h"
+#include "openmc/search.h"
 
 namespace openmc {
 
diff --git a/src/secondary_kalbach.cpp b/src/secondary_kalbach.cpp
index e8941ff93d..3e79072100 100644
--- a/src/secondary_kalbach.cpp
+++ b/src/secondary_kalbach.cpp
@@ -1,4 +1,4 @@
-#include "secondary_kalbach.h"
+#include "openmc/secondary_kalbach.h"
 
 #include <algorithm> // for copy, move
 #include <cmath>     // for log, sqrt, sinh
@@ -8,9 +8,10 @@
 
 #include "xtensor/xarray.hpp"
 #include "xtensor/xview.hpp"
-#include "hdf5_interface.h"
-#include "random_lcg.h"
-#include "search.h"
+
+#include "openmc/hdf5_interface.h"
+#include "openmc/random_lcg.h"
+#include "openmc/search.h"
 
 namespace openmc {
 
diff --git a/src/secondary_nbody.cpp b/src/secondary_nbody.cpp
index 44a66c6bd1..45f6d3cb86 100644
--- a/src/secondary_nbody.cpp
+++ b/src/secondary_nbody.cpp
@@ -1,11 +1,11 @@
-#include "secondary_nbody.h"
+#include "openmc/secondary_nbody.h"
 
 #include <cmath> // for log
 
-#include "constants.h"
-#include "hdf5_interface.h"
-#include "math_functions.h"
-#include "random_lcg.h"
+#include "openmc/constants.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/math_functions.h"
+#include "openmc/random_lcg.h"
 
 namespace openmc {
 
diff --git a/src/secondary_uncorrelated.cpp b/src/secondary_uncorrelated.cpp
index df5e8139b9..3192c1e04c 100644
--- a/src/secondary_uncorrelated.cpp
+++ b/src/secondary_uncorrelated.cpp
@@ -1,11 +1,11 @@
-#include "secondary_uncorrelated.h"
+#include "openmc/secondary_uncorrelated.h"
 
 #include <sstream> // for stringstream
 #include <string>  // for string
 
-#include "error.h"
-#include "hdf5_interface.h"
-#include "random_lcg.h"
+#include "openmc/error.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/random_lcg.h"
 
 namespace openmc {
 
diff --git a/src/settings.cpp b/src/settings.cpp
index c705ef8a74..b23013c317 100644
--- a/src/settings.cpp
+++ b/src/settings.cpp
@@ -1,10 +1,10 @@
-#include "settings.h"
+#include "openmc/settings.h"
 
-#include "constants.h"
-#include "error.h"
-#include "openmc.h"
-#include "string_utils.h"
-#include "xml_interface.h"
+#include "openmc/capi.h"
+#include "openmc/constants.h"
+#include "openmc/error.h"
+#include "openmc/string_utils.h"
+#include "openmc/xml_interface.h"
 
 namespace openmc {
 
diff --git a/src/simulation.cpp b/src/simulation.cpp
index e9bf81775a..e1dd0ac934 100644
--- a/src/simulation.cpp
+++ b/src/simulation.cpp
@@ -1,4 +1,4 @@
-#include "openmc.h"
+#include "openmc/capi.h"
 
 // OPENMC_RUN encompasses all the main logic where iterations are performed
 // over the batches, generations, and histories in a fixed source or k-eigenvalue
diff --git a/src/state_point.cpp b/src/state_point.cpp
index 4e6b9a9f9f..1e4c8bdfd4 100644
--- a/src/state_point.cpp
+++ b/src/state_point.cpp
@@ -1,4 +1,4 @@
-#include "state_point.h"
+#include "openmc/state_point.h"
 
 #include <algorithm>
 #include <vector>
@@ -6,9 +6,10 @@
 #ifdef OPENMC_MPI
 #include "mpi.h"
 #endif
-#include "error.h"
-#include "message_passing.h"
-#include "openmc.h"
+
+#include "openmc/capi.h"
+#include "openmc/error.h"
+#include "openmc/message_passing.h"
 
 namespace openmc {
 
diff --git a/src/string_functions.cpp b/src/string_functions.cpp
index f41ec40c1e..f81b09aef4 100644
--- a/src/string_functions.cpp
+++ b/src/string_functions.cpp
@@ -1,4 +1,4 @@
-#include "string_functions.h"
+#include "openmc/string_functions.h"
 
 namespace openmc {
 
@@ -27,4 +27,4 @@ void to_lower(std::string& str)
   for (int i = 0; i < str.size(); i++) str[i] = std::tolower(str[i]);
 }
 
-} // namespace openmc
\ No newline at end of file
+} // namespace openmc
diff --git a/src/surface.cpp b/src/surface.cpp
index 421c43d485..78f2302e53 100644
--- a/src/surface.cpp
+++ b/src/surface.cpp
@@ -1,13 +1,13 @@
-#include "surface.h"
+#include "openmc/surface.h"
 
 #include <array>
 #include <cmath>
 #include <sstream>
 #include <utility>
 
-#include "error.h"
-#include "hdf5_interface.h"
-#include "xml_interface.h"
+#include "openmc/error.h"
+#include "openmc/hdf5_interface.h"
+#include "openmc/xml_interface.h"
 
 
 namespace openmc {
diff --git a/src/thermal.cpp b/src/thermal.cpp
index 2732b8f02a..b63d2e6d16 100644
--- a/src/thermal.cpp
+++ b/src/thermal.cpp
@@ -1,4 +1,4 @@
-#include "thermal.h"
+#include "openmc/thermal.h"
 
 #include <algorithm> // for sort, move, min, max, find
 #include <cmath>     // for round, sqrt, fabs
@@ -11,12 +11,12 @@
 #include "xtensor/xtensor.hpp"
 #include "xtensor/xview.hpp"
 
-#include "constants.h"
-#include "error.h"
-#include "random_lcg.h"
-#include "search.h"
-#include "secondary_correlated.h"
-#include "settings.h"
+#include "openmc/constants.h"
+#include "openmc/error.h"
+#include "openmc/random_lcg.h"
+#include "openmc/search.h"
+#include "openmc/secondary_correlated.h"
+#include "openmc/settings.h"
 
 namespace openmc {
 
diff --git a/src/xml_interface.cpp b/src/xml_interface.cpp
index 5835c8600a..18627efe38 100644
--- a/src/xml_interface.cpp
+++ b/src/xml_interface.cpp
@@ -1,9 +1,9 @@
-#include "xml_interface.h"
+#include "openmc/xml_interface.h"
 
 #include <algorithm>  // for transform
 #include <sstream>
 
-#include "error.h"
+#include "openmc/error.h"
 
 
 namespace openmc {
diff --git a/src/xsdata.cpp b/src/xsdata.cpp
index 3482a316a2..d9863694a7 100644
--- a/src/xsdata.cpp
+++ b/src/xsdata.cpp
@@ -1,13 +1,14 @@
+#include "openmc/xsdata.h"
+
 #include <cmath>
 #include <cstdlib>
 #include <algorithm>
 #include <numeric>
 
-#include "constants.h"
-#include "error.h"
-#include "math_functions.h"
-#include "random_lcg.h"
-#include "xsdata.h"
+#include "openmc/constants.h"
+#include "openmc/error.h"
+#include "openmc/math_functions.h"
+#include "openmc/random_lcg.h"
 
 
 namespace openmc {