The following images show graffiti on Alcatraz Island left behind by federal penitentiary convicts and U.S. Army prisoners. Many of these carvings are found in the "dark" cells on the top tier of A Block, carved into the floors near ventilation holes in the doors that allowed a small amounts of light to trickle in. These cells appear to have been used extensively for housing BOP inmates prior to the completion of modern "D Block" in 1941.