USS Philadelphia, a 505-ton (burden) iron-hulled side-wheel steamship, was built at Chester, Pennsylvania, in 1859 as the commercial vessel of the same name. She was seized in April 1861, as the Civil War was beginning, and placed in service to patrol the Potomac River area. At times during the war's first six months she was also employed on transport duty in the Chesapeake Bay area and along the Central Atlantic Seaboard. After October 1861 Philadelphia served in the Atlantic, initially taking part in operations along the coast of North Carolina. She participated in the capture of several important Confederate positions during early 1862.

Philadelphia was transferred to the South Atlantic Blockading Squadron in August 1863. For the rest of the Civil War she was frequently employed as that Squadron's flagship and participated in operations against Charleston, South Carolina, during some of this time. Decommissioned at Washington, D.C., at the end of August 1865, the ship was sold in mid-September. She soon returned to civilian trade, keeping her original name. Renamed Ironsides in 1869, she was lost by stranding at Hog Island, Virginia, on 29 August 1873.