It is located in southern San Joaquin County southwest of the town of Ripon.

This park has been named after the landowner, Thomas Caswell.

In the 1950s, 134 acres (54 ha) of this forest were donated by his children and grandchildren to California before it was opened to the public as a state park in 1958.

[2] The riparian brush rabbit (S. b. riparius) is listed as an endangered species by the United States Fish and Wildlife Service.

[4] This population has been negatively impacted by the destruction of the riparian habitat.