Fort Townsend was built in 1856 by the U.S. Army to protect settlers. The entire garrison was transferred to the American Camp or Camp Pickett on San Juan Island in 1859 during the border dispute called the Pig War. Reactivated in 1874, the fort continued in use until fire destroyed the barracks in late 1894; it was abandoned in 1895. The site was retained on the Army rolls until World War II, when it was used as a munitions defusing station. Washington State Parks took custody in 1953, and it became a state park.