Old Dubuque County Jail was built in 1857 by architect John Francis Rague and constructed between February 1857 and the spring of 1858 at a cost of $40,000. One of only three surviving Egyptian Revival buildings in the United States, it is listed on the National Register of Historic Places and is also an official National Historic Landmark. The building was made with 18-inch-thick gray limestone walls, with cast iron used for window and door frames and decorative columns. A two-story square section provided living quarters for the sheriff's family, while the jail itself stood between those quarters and the county courthouse. Three tiers of cells lined the eastern wall, with a catwalk to the upper cells, and a basement cell block with a curved ceiling held Confederate prisoners during the Civil War before later being used for troublesome prisoners. In 1874, six cells were added for juveniles and women prisoners. The building ceased functioning as a jail in 1971. The Dubuque Art Association leased it in 1975 for museum use, although the county's juvenile probation offices still occupied part of it, and remained there until 2003, when it moved to a renovated modern style bank building across from Washington Park. Since then, the Dubuque County Historical Society has owned and operated the building as the Old Jail Museum, displaying artifacts.