The website is in error. Camp Townsend was a site used for prisoner-of-war exchange in 1865. Military service cards for Confederate prisoners of war will show departure from Ship Island, Miss., Apr. 28, 1865, transportation from New Orleans, La., to Vicksburg, Miss., May 1, 1865, and exchange at Camp Townsend on the Big Black River, six miles east of Vicksburg, May 6, 1865.

Some of this can be found in the fine print at the bottom of the service cards. The War Department must have printed a large batch of these for all Confederates at Ship Island who were released when the war ended. Let me know if I'm mistaken, since this is purely from memory.