The Cairo is the sole survivor of the fleet of river gunboats built by the Union during the Civil War with the object of controlling the lower Mississippi River. Designed by Samuel Pook and built by James B. Eads, it saw limited battle and was sunk on the Yazoo River in 1862 by newly developed electronically detonated mines, becoming the first craft ever sunk by this predecessor to torpedo technology. The 175-foot ironclad vessel had 13 guns.
In the decade following the Civil War, the Mississippi River began to lose its standing as the primary transport artery in the Midwest. Railroads were taking over, and Chicago was rapidly becoming the center of Midwestern commerce. The Eads Bridge was the first major railroad link over the Mississippi, constructed by the city of St. Louis in an attempt to maintain its dominance as a regional commercial hub.