The U.S.S. Cairo was one of seven ironclad gunboats named in honor of towns along the upper Mississippi and Ohio rivers. These powerful ironclads were formidable vessels, each mounting thirteen big guns (cannon). On them rested in large part, Northern hopes to regain control of the lower Mississippi River and split the Confederacy in two.

The "city class" gunboats were designed by Samuel M. Pook and built by river engineer James B. Eads. Cairo was constructed at Mound City, Illinois, and commissioned in January 1862. The Cairo was destined to see only limited action in the engagement at Plum Point in May and in the battle of Memphis in June. Her most significant action came six months later when she kept a rendezvous with destiny.