On 20 March 1864, Glennan entered Camp Sumter, located near Andersonville, Georgia. He reminisced about the events of his eight-month captivity at Andersonville, such as the hanging of the Raider Six, escape tunnels, gambling, trading, ration wagons, and disease. Afflicted with scurvy, Glennan nearly lost his ability to walk. To increase his chances for survival, he skillfully befriended other prisoners, sharing resources acquired through trade, theft and trickery. His friends left him either by parole or death. On 14 November 1864, Glennan was transported from Andersonville to Camp Parole in Maryland; there he remained until his discharge on 4 June 1865.