USS Keystone State , a 1364-ton side wheel steamship, was built at Philadelphia, Pennsylvania, in 1853 as the civilian steamer Keystone State. Chartered by the Navy in April 1861, as the Civil War began, she captured one suspected blockade runner in May. Purchased after the charter period ended, she was placed in commission a month later. For the rest of that year, Keystone State cruised in the Atlantic and Caribbean areas.

Operations with the South Atlantic Blockading Squadron began in January 1862, and Keystone State took part the seizure of positions along the Florida and Georga coasts during March 1862. Mainly, however, she patrolled offshore, capturing several blockade runners. While stationed off Charleston, South Carolina, on 31 January 1863, Keystone State was disabled while engaging the Confederate ironclads Chicora and Palmetto State. Repaired locally, she remained in service until June 1863, then went north for an overhaul.

Keystone State returned to active duty in October 1863 and served thereafter with the North Atlantic Blockading Squadron, mainly off the North Carolina coast. From November 1863 until September 1864 she took or helped take six more blockade running steamships, assisted in the destruction of another and recovered a large number of cotton bales. She was part of the fleet that assaulted Fort Fisher, North Carolina, in December 1864 and captured it in January 1865. After a few months of additional operations USS Keystone State was decommissioned in March 1865. She was sold in September of that year.

USS Keystone State