USS Baron DeKalb was a City-class ironclad gunboat constructed for the Union Navy by James B. Eads during the American Civil War.

Called "Pook Turtles" for the designer, they did yeoman service through four years of war and were present at almost every battle on the Mississippi River and its tributaries.

During 1862 St. Louis, under the command of Lieutenant L. Paulding USN, was attached to Rear Admiral Andrew Hull Foote's squadron and participated in the Battle of Lucas Bend and the capture of Fort Henry on the Tennessee River (February 6, 1862).

She served as flagship for the squadron when it assisted the Union Army at the capture of Fort Donelson on the Cumberland River (February 14–16, 1862).

Like many of the Mississippi theater ironclads, Baron Dekalb had its armament changed multiple times over life of the vessel.