The Sally Port was the only entrance to the Fort, reached by crossing a 1,100 foot wooden causeway from the island, and all personnel and goods entered and exited through it while a moat and drawbridge protected the Fort from unauthorized access. On the morning of January 14, 1861, Captain John M. Brannan led troops of Battery B, 1st U.S. Artillery, quietly across the island from the U.S. Army Barrack to Fort Taylor, bringing four 6-pounder field guns, ammunition and muskets. They crossed the causeway and entered the Fort unchallenged, and the Union flag that had flown above the U.S. Army Barrack was raised above the Fort, showing the islanders that it was in Union hands. The Fort then remained under Union control for the duration of the American Civil War. Prison cells stood on each side of the Sally Port, where soldiers, sailors and blockade runners were often held until they could be tried on their charges. In July 1865, Dr. Samuel Mudd and other conspirators of President Abraham Lincoln were held there briefly before being transferred to Fort Jefferson in the Dry Tortugas.