The John Singleton Mosby Foundation, Inc., was established by a group of Warrenton citizens to preserve the National Register of Historic Places property called Brentmoor. Since the house was once the home of Colonel John Singleton Mosby and the town formed part of "Mosby's Confederacy," these several community members believed that Brentmoor could become the home of a museum interpreting Mosby and Warrenton's Civil War experience. Founded in 1998, the John Singleton Mosby Foundation, Inc. is a non-profit membership association dedicated to the preservation of Brentmoor and the creation of the Mosby Museum.

Acquisition and preservation of Brentmoor . Present the history of the notable owners Colonel John S, Mosby, Judge Edward Spiman, Judge James Keith, and Brigadier General Eppa Hunton. Collect artifacts, decorate arts and archival materials documenting he historic house, its owners, and Warrenton's Civil War heritage. Restore the three buildings located on this National Register of Historic Places property Establish a Civil War Education Center to include the preserntation of 'Standards of Learning' interactive learning sessions for local schools. Create a park and restore the historic gardens on the grounds of Brentmoor .