diff --git a/docs/source/capi/index.rst b/docs/source/capi/index.rst
index ff19758bb3..d63ed1f3ae 100644
--- a/docs/source/capi/index.rst
+++ b/docs/source/capi/index.rst
@@ -4,6 +4,48 @@
 C API
 =====
 
+The libopenmc shared library that is built when installing OpenMC exports a
+number of C interoperable functions and global variables that can be used for
+in-memory coupling. While it is possible to directly use the C API as documented
+here for coupling, most advanced users will find it easier to work with the
+Python bindings in the :py:mod:`openmc.capi` module.
+
+.. warning:: The C API is still experimental and may undergo substantial changes
+             in future releases.
+
+----------------
+Type Definitions
+----------------
+
+.. c:type:: Bank
+
+   Attributes of a source particle.
+
+   .. c:member:: double wgt
+
+      Weight of the particle
+
+   .. c:member:: double xyz[3]
+
+      Position of the particle (units of cm)
+
+   .. c:member:: double uvw[3]
+
+      Unit vector indicating direction of the particle
+
+   .. c:member:: double E
+
+      Energy of the particle in eV
+
+   .. c:member:: int delayed_group
+
+      If the particle is a delayed neutron, indicates which delayed precursor
+      group it was born from. If not a delayed neutron, this member is zero.
+
+---------
+Functions
+---------
+
 .. c:function:: void openmc_calculate_volumes()
 
    Run a stochastic volume calculation
@@ -15,7 +57,7 @@ C API
    :param int32_t index: Index in the cells array
    :param int* type: Type of the fill
    :param int32_t** indices: Array of material indices for cell
-   :param int32_t n: Length of indices array
+   :param int32_t* n: Length of indices array
    :return: Return status (negative if an error occurred)
    :rtype: int
 
@@ -28,14 +70,15 @@ C API
    :return: Return status (negative if an error occurred)
    :rtype: int
 
-.. c:function:: int openmc_cell_set_fill(int32_t index, int type, int32_t n, int32_t* indices)
+.. c:function:: int openmc_cell_set_fill(int32_t index, int type, int32_t n, const int32_t* indices)
 
    Set the fill for a cell
 
    :param int32_t index: Index in the cells array
    :param int type: Type of the fill
    :param int32_t n: Length of indices array
-   :param int32_t* indices: Array of material indices for cell
+   :param indices: Array of material indices for cell
+   :type indices: const int32_t*
    :return: Return status (negative if an error occurred)
    :rtype: int
 
@@ -48,14 +91,15 @@ C API
    :return: Return status (negative if an error occurred)
    :rtype: int
 
-.. c:function:: int openmc_cell_set_temperature(index index, double T, int32_t* instance)
+.. c:function:: int openmc_cell_set_temperature(index index, double T, const int32_t* instance)
 
    Set the temperature of a cell.
 
    :param int32_t index: Index in the cells array
    :param double T: Temperature in Kelvin
-   :param int32_t* instance: Which instance of the cell. To set the temperature
-                             for all instances, pass a null pointer.
+   :param instance: Which instance of the cell. To set the temperature for all
+                    instances, pass a null pointer.
+   :type instance: const int32_t*
    :return: Return status (negative if an error occurred)
    :rtype: int
 
@@ -69,13 +113,14 @@ C API
    :return: Return status (negative if an error occurred)
    :rtype: int
 
-.. c:function:: int openmc_energy_filter_set_bins(int32_t index, int32_t n, double* energies)
+.. c:function:: int openmc_energy_filter_set_bins(int32_t index, int32_t n, const double* energies)
 
    Set the bounding energies for an energy filter
 
    :param int32_t index: Index in the filters array
    :param int32_t n: Number of energies specified
-   :param double* energies: Bounding energies of the bins for the energy filter
+   :param energies: Bounding energies of the bins for the energy filter
+   :type energies: const double*
    :return: Return status (negative if an error occurred)
    :rtype: int
 
@@ -109,6 +154,16 @@ C API
    :return: Return status (negative if an error occurred)
    :rtype: int
 
+.. c:function:: int openmc_extend_sources(int32_t n, int32_t* index_start, int32_t* index_end)
+
+   Extend the external sources array by n elements
+
+   :param int32_t n: Number of sources to create
+   :param int32_t* index_start: Index of first new source
+   :param int32_t* index_end: Index of last new source
+   :return: Return status (negative if an error occurred)
+   :rtype: int
+
 .. c:function:: int openmc_extend_tallies(int32_t n, int32_t* index_start, int32_t* index_end)
 
    Extend the tallies array by n elements
@@ -150,7 +205,7 @@ C API
    :param int32_t* id: ID of the cell/material found. If a material is requested
                        and the point is in a void, the ID is 0. If an error
                        occurs, the ID is -1.
-   :param int32_t* instance: If a cell is repetaed in the geometry, the instance
+   :param int32_t* instance: If a cell is repeated in the geometry, the instance
                              of the cell that was found and zero otherwise.
 
 .. c:function:: int openmc_get_cell_index(int32_t id, int32_t* index)
@@ -177,7 +232,7 @@ C API
 
    :param int32_t* id: Unused integer ID
 
-.. c:function:: int openmc_get_keff(double k_combined[])
+.. c:function:: int openmc_get_keff(double k_combined[2])
 
    :param double[2] k_combined: Combined estimate of k-effective
    :return: Return status (negative if an error occurs)
@@ -214,11 +269,13 @@ C API
 
    Reset tallies, timers, and pseudo-random number generator state
 
-.. c:function:: void openmc_init(int intracomm)
+.. c:function:: void openmc_init(const int* intracomm)
 
    Initialize OpenMC
 
-   :param int intracomm: MPI intracommunicator
+   :param intracomm: MPI intracommunicator. If MPI is not being used, a null
+                     pointer should be passed.
+   :type intracomm: const int*
 
 .. c:function:: int openmc_load_nuclide(char name[])
 
@@ -228,18 +285,19 @@ C API
    :return: Return status (negative if an error occurs)
    :rtype: int
 
-.. c:function:: int openmc_material_add_nuclide(int32_t index, char name[], double density)
+.. c:function:: int openmc_material_add_nuclide(int32_t index, const char name[], double density)
 
    Add a nuclide to an existing material. If the nuclide already exists, the
    density is overwritten.
 
    :param int32_t index: Index in the materials array
-   :param char[] name: Name of the nuclide
+   :param name: Name of the nuclide
+   :type name: const char[]
    :param double density: Density in atom/b-cm
    :return: Return status (negative if an error occurs)
    :rtype: int
 
-.. c:function:: int openmc_material_get_densities(int32_t index, int* nuclides[], double* densities[], int* n)
+.. c:function:: int openmc_material_get_densities(int32_t index, int** nuclides, double** densities, int* n)
 
    Get density for each nuclide in a material.
 
@@ -268,12 +326,14 @@ C API
    :return: Return status (negative if an error occurs)
    :rtype: int
 
-.. c:function:: int openmc_material_set_densities(int32_t index, int n, char* name[], double density[])
+.. c:function:: int openmc_material_set_densities(int32_t index, int n, const char** name, const double density*)
 
    :param int32_t index: Index in the materials array
    :param int n: Length of name/density
-   :param char** name: Array of nuclide names
-   :param double[] density: Array of densities
+   :param name: Array of nuclide names
+   :type name: const char**
+   :param density: Array of densities
+   :type density: const double*
    :return: Return status (negative if an error occurs)
    :rtype: int
 
@@ -296,13 +356,14 @@ C API
    :return: Return status (negative if an error occurred)
    :rtype: int
 
-.. c:function:: int openmc_material_filter_set_bins(int32_t index, int32_t n, int32_t* bins)
+.. c:function:: int openmc_material_filter_set_bins(int32_t index, int32_t n, const int32_t* bins)
 
    Set the bins for a material filter
 
    :param int32_t index: Index in the filters array
    :param int32_t n: Number of bins
-   :param int32_t* bins: Index in the materials array for each bin
+   :param bins: Index in the materials array for each bin
+   :type bins: const int32_t*
    :return: Return status (negative if an error occurred)
    :rtype: int
 
@@ -323,7 +384,7 @@ C API
             finished (zero).
    :rtype: int
 
-.. c:function:: int openmc_nuclide_name(int index, char* name[])
+.. c:function:: int openmc_nuclide_name(int index, char** name)
 
    Get name of a nuclide
 
@@ -352,6 +413,33 @@ C API
 
    Initialize a simulation. Must be called after openmc_init().
 
+.. c:function:: int openmc_source_bank(struct Bank** ptr, int64_t* n)
+
+   Return a pointer to the source bank array.
+
+   :param ptr: Pointer to the source bank array
+   :type ptr: struct Bank**
+   :param int64_t* n: Length of the source bank array
+   :return: Return status (negative if an error occurred)
+   :rtype: int
+
+.. c:function:: int openmc_source_set_strength(int32_t index, double strength)
+
+   Set the strength of an external source
+
+   :param int32_t index: Index in the external source array
+   :param double strength: Source strength
+   :return: Return status (negative if an error occurred)
+   :rtype: int
+
+.. c:function:: void openmc_statepoint_write(const char filename[])
+
+   Write a statepoint file
+
+   :param filename: Name of file to create. If a null pointer is passed, a
+                    filename is assigned automatically.
+   :type filename: const char[]
+
 .. c:function:: int openmc_tally_get_id(int32_t index, int32_t* id)
 
    Get the ID of a tally
@@ -378,7 +466,7 @@ C API
    :return: Return status (negative if an error occurred)
    :rtype: int
 
-.. c:function:: int openmc_tally_get_nuclides(int32_t index, int* nuclides[], int* n)
+.. c:function:: int openmc_tally_get_nuclides(int32_t index, int** nuclides, int* n)
 
    Get nuclides specified in a tally
 
@@ -408,13 +496,14 @@ C API
    :return: Return status (negative if an error occurred)
    :rtype: int
 
-.. c:function:: int openmc_tally_set_filters(int32_t index, int n, int32_t* indices)
+.. c:function:: int openmc_tally_set_filters(int32_t index, int n, const int32_t* indices)
 
    Set filters for a tally
 
    :param int32_t index: Index in the tallies array
    :param int n: Number of filters
-   :param int32_t* indices: Array of filter indices
+   :param indices: Array of filter indices
+   :type indices: const int32_t*
    :return: Return status (negative if an error occurred)
    :rtype: int
 
@@ -427,22 +516,24 @@ C API
    :return: Return status (negative if an error occurred)
    :rtype: int
 
-.. c:function:: int openmc_tally_set_nuclides(int32_t index, int n, char* nuclides[])
+.. c:function:: int openmc_tally_set_nuclides(int32_t index, int n, const char** nuclides)
 
    Set the nuclides for a tally
 
    :param int32_t index: Index in the tallies array
    :param int n: Number of nuclides
-   :param char** nuclides: Array of nuclide names
+   :param nuclides: Array of nuclide names
+   :type nuclides: const char**
    :return: Return status (negative if an error occurred)
    :rtype: int
 
-.. c:function:: int openmc_tally_set_scores(int32_t index, int n, int* scores)
+.. c:function:: int openmc_tally_set_scores(int32_t index, int n, const int* scores)
 
    Set scores for a tally
 
    :param int32_t index: Index in the tallies array
    :param int n: Number of scores
-   :param int* scores: Array of scores
+   :param scores: Array of scores
+   :type scores: const int*
    :return: Return status (negative if an error occurred)
    :rtype: int
diff --git a/include/openmc.h b/include/openmc.h
index 5f72e99ed2..bb04907a52 100644
--- a/include/openmc.h
+++ b/include/openmc.h
@@ -8,29 +8,30 @@
 extern "C" {
 #endif
 
-  void openmc_calculate_voumes();
-  void openmc_finalize();
-  void openmc_hard_reset();
-  int openmc_next_batch();
-  void openmc_plot_geometry();
-  void openmc_reset();
-  void openmc_run();
-  void openmc_simulation_finalize();
-  void openmc_simulation_init();
+  struct Bank {
+    double wgt;
+    double xyz[3];
+    double uvw[3];
+    double E;
+    int delayed_group;
+  };
 
+  void openmc_calculate_voumes();
   int openmc_cell_get_fill(int32_t index, int* type, int32_t** indices, int32_t* n);
   int openmc_cell_get_id(int32_t index, int32_t* id);
-  int openmc_cell_set_fill(int32_t index, int type, int32_t n, int32_t* indices);
+  int openmc_cell_set_fill(int32_t index, int type, int32_t n, const int32_t* indices);
   int openmc_cell_set_id(int32_t index, int32_t id);
-  int openmc_cell_set_temperature(int32_t index, double T, int32_t* instance);
+  int openmc_cell_set_temperature(int32_t index, double T, const int32_t* instance);
   int openmc_energy_filter_get_bins(int32_t index, double** energies, int32_t* n);
-  int openmc_energy_filter_set_bins(int32_t index, int32_t n, double* energies);
+  int openmc_energy_filter_set_bins(int32_t index, int32_t n, const double* energies);
   int openmc_extend_cells(int32_t n, int32_t* index_start, int32_t* index_end);
   int openmc_extend_filters(int32_t n, int32_t* index_start, int32_t* index_end);
   int openmc_extend_materials(int32_t n, int32_t* index_start, int32_t* index_end);
+  int openmc_extend_sources(int32_t n, int32_t* index_start, int32_t* index_end);
   int openmc_extend_tallies(int32_t n, int32_t* index_start, int32_t* index_end);
   int openmc_filter_get_id(int32_t index, int32_t* id);
   int openmc_filter_set_id(int32_t index, int32_t id);
+  void openmc_finalize();
   int openmc_find(double* xyz, int rtype, int32_t* id, 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);
@@ -38,28 +39,39 @@ extern "C" {
   int openmc_get_keff(double k_combined[]);
   int openmc_get_material_index(int32_t id, int32_t* index);
   int openmc_get_nuclide_index(char name[], int* index);
-  int openmc_get_tally_tally(int32_t id, int32_t* index);
+  int openmc_get_tally_index(int32_t id, int32_t* index);
+  void openmc_hard_reset();
+  void openmc_init(const int* intracomm);
   int openmc_load_nuclide(char name[]);
-  int openmc_material_add_nuclide(int32_t index, char name[], double density);
-  int openmc_material_get_densities(int32_t index, int* nuclides[], double* densities[], int* n);
+  int openmc_material_add_nuclide(int32_t index, const char name[], double density);
+  int openmc_material_get_densities(int32_t index, int** nuclides, double** densities, int* n);
   int openmc_material_get_id(int32_t index, int32_t* id);
   int openmc_material_set_density(int32_t index, double density);
-  int openmc_material_set_densities(int32_t index, int n, char* name[], double density[]);
+  int openmc_material_set_densities(int32_t index, int n, const char** name, const double* density);
   int openmc_material_set_id(int32_t index, int32_t id);
   int openmc_material_filter_get_bins(int32_t index, int32_t** bins, int32_t* n);
-  int openmc_material_filter_set_bins(int32_t index, int32_t n, int32_t* bins);
+  int openmc_material_filter_set_bins(int32_t index, int32_t n, const int32_t* bins);
   int openmc_mesh_filter_set_mesh(int32_t index, int32_t index_mesh);
-  int openmc_nuclide_name(int index, char* name[]);
+  int openmc_next_batch();
+  int openmc_nuclide_name(int index, char** name);
+  void openmc_plot_geometry();
+  void openmc_reset();
+  void openmc_run();
+  void openmc_simulation_finalize();
+  void openmc_simulation_init();
+  int openmc_source_bank(struct Bank** ptr, int64_t* n);
+  int openmc_source_set_strength(int32_t index, double strength);
+  void openmc_statepoint_write(const char filename[]);
   int openmc_tally_get_id(int32_t index, int32_t* id);
   int openmc_tally_get_filters(int32_t index, int32_t** indices, int* n);
   int openmc_tally_get_n_realizations(int32_t index, int32_t* n);
-  int openmc_tally_get_nuclides(int32_t index, int* nuclides[], int* n);
+  int openmc_tally_get_nuclides(int32_t index, int** nuclides, int* n);
   int openmc_tally_get_scores(int32_t index, int** scores, int* n);
   int openmc_tally_results(int32_t index, double** ptr, int shape_[3]);
-  int openmc_tally_set_filters(int32_t index, int n, int32_t* indices);
+  int openmc_tally_set_filters(int32_t index, int n, const int32_t* indices);
   int openmc_tally_set_id(int32_t index, int32_t id);
-  int openmc_tally_set_nuclides(int32_t index, int n, char* nuclides[]);
-  int openmc_tally_set_scores(int32_t index, int n, int* scores);
+  int openmc_tally_set_nuclides(int32_t index, int n, const char** nuclides);
+  int openmc_tally_set_scores(int32_t index, int n, const int* scores);
 
   // Error codes
   extern int E_UNASSIGNED;
diff --git a/src/api.F90 b/src/api.F90
index 9db06ac205..eb9a996950 100644
--- a/src/api.F90
+++ b/src/api.F90
@@ -4,6 +4,7 @@ module openmc_api
 
   use hdf5, only: HID_T, h5tclose_f, h5close_f
 
+  use bank_header,     only: openmc_source_bank
   use constants,       only: K_BOLTZMANN
   use eigenvalue,      only: k_sum, openmc_get_keff
   use error
@@ -20,6 +21,8 @@ module openmc_api
   use random_lcg,      only: seed, openmc_set_seed
   use settings
   use simulation_header
+  use source_header,   only: openmc_extend_sources, openmc_source_set_strength
+  use state_point,     only: openmc_statepoint_write
   use tally_header
   use tally_filter_header
   use tally_filter
@@ -43,6 +46,7 @@ module openmc_api
   public :: openmc_extend_filters
   public :: openmc_extend_cells
   public :: openmc_extend_materials
+  public :: openmc_extend_sources
   public :: openmc_extend_tallies
   public :: openmc_filter_get_id
   public :: openmc_filter_get_type
@@ -77,6 +81,8 @@ module openmc_api
   public :: openmc_run
   public :: openmc_simulation_finalize
   public :: openmc_simulation_init
+  public :: openmc_source_bank
+  public :: openmc_source_set_strength
   public :: openmc_tally_get_id
   public :: openmc_tally_get_filters
   public :: openmc_tally_get_n_realizations
diff --git a/src/source_header.F90 b/src/source_header.F90
index fca05d8167..da15046ab8 100644
--- a/src/source_header.F90
+++ b/src/source_header.F90
@@ -17,6 +17,8 @@ module source_header
   implicit none
   private
   public :: free_memory_source
+  public :: openmc_extend_sources
+  public :: openmc_source_set_strength
 
   integer :: n_accept = 0  ! Number of samples accepted
   integer :: n_reject = 0  ! Number of samples rejected