At the start of the American Civil War, neither side had warships on the Mississippi River and in the first few months both sides scrambled to gather a flotilla, converting existing riverboats for naval use. These ships were transformed into powerful naval weapons despite a lack of resources, trained manpower and suitable vessels. The creation of a river fleet was a miracle of ingenuity, improvisation and logistics, particularly for the South. This title describes their design, development and operation throughout the American Civil War.

Once the Union Army gained control of the upper rivers of the Mississippi Valley during the first half of 1862, slow and heavy ironclads proved ineffective in patrolling the waters. Hastily outfitted steamboats were covered with thin armor and pressed into duty. These "tinclads" fought Confederate forces attacking from the riverbanks, provided convoy for merchant steamers, enforced revenue measures, and offered tow, dispatch, and other fleet support services. This history documents the service records and duties of these little-known vessels of the Union fleet.