Cairo, Illinois, and the building of the Eads bridge

This article about the contribution of Cairo, Illinois, to building the Eads bridge demonstrates that what may appear insignificant at one time can have profound effects another time.

Cairo is located at the tip of Southern Illinois at the confluence of the Ohio and Mississippi rivers. Founded in 1818, it became the terminus for the Illinois Central Railroad by 1855. By 1861 the U.S. was in a Civil War, and by September the Union Army made Cairo the naval station for the Mississippi River Squadron, making the city an important base of operation for Union forces for the rest of the war.

James Buchanan Eads was born in Lawrenceburg, Indiana, in 1820 and moved to St. Louis in 1833. He left school at the age of 13 to help support his family after his father left. Eads was mostly self-educated, learning from reading books on mechanics, science and civil engineering in the upstairs library of his first employer, Barrett Williams. At the time of his death in 1887, Eads held 50 patents and was worth $500,000 ($16 million today).

In 1842, Eads became partners in a salvage business working the Mississippi River from Iowa to New Orleans. Eads had designed what he called a diving bell from a 40-gallon wine barrel that allowed him to walk on the bottom of the Mississippi, breathing compressed air, recovering items from sunken boats. Eads continued his salvage work assisting the Union Army in retrieving sunken war vessels and material during the Civil War. Eads learned during his walks on the river bottom at Cairo how the river could scour rocks, along with discovering the riverbed consisted of shifting layers of sand and mud on top of blue shale which rested on top of the bedrock.

After the Civil War, ended St. Louis wanted a railroad bridge to Illinois to connect to the growing railroad traffic. Eads submitted a proposal of a steel arched bridge for rail and foot traffic to the St. Louis Bridge and Iron C., formed in 1867 for the purpose of building the bridge. A bridge like Eads' had never been built in the United States, plus Eads had never built a bridge, making the city skeptical. The engineer the city was considering, Lucious Boomer of Chicago, had built a railroad bridge across the Gasconade River, which collapsed in 1855 because the piers had been set in mud, not on bedrock. Setting the piers on bedrock was one of Eads' strongest arguments as to why he should be hired to build the bridge. Public opinion got behind Eads, and Boomer withdrew, allowing Eads to receive the contract. The bridge opened July 2, 1874, setting several engineering firsts for its design, and after almost 150 years is still in use today.

The discoveries Eads made at Cairo of the river's shifting power with sand and mud, along with the importance of removing the blue shale to connect the piers to bedrock, led to creating solid foundations to support a record-setting bridge.