Built in 1876 and in use until 1945, the granite block and brick structure retains its original upstairs cells where prisoners were once segregated by gender and race. The jail keeper's quarters downstairs house artifacts that relate county history. A cannon from The Ark, one of two ships that first brought colonists to Maryland, and later used to defend St. Mary's City, is displayed on the grounds. The museum also serves as a county visitor information center. Special tours and hours are available by advanced arrangement.
National Park Service Underground Railroad Network to Freedom site. The Old Jail was built in 1858 and was in use through the early 1940s. Runaway slaves were often held in public jails until their owners retrieved them or they were sold in compensation for the cost of care. Five stories of runaway slaves are connected with this jail. Today the building houses exhibits of the St. Mary’s County Historical Society and serves as a county visitor information center.