Jody Victor : Louisville, Kentucky was founded at the only major natural navigational barrier on the river, the Falls of the Ohio. The Falls were a series of rapids where the river dropped 26 feet in a stretch of about 2 miles. In this area the river flowed over hard, fossil-rich beds of limestone. The first locks on the river were built at Louisville in 1825 to circumnavigate the falls. Today it is the site of McAlpine Locks and Dam.
Because the Ohio River flowed westwardly, it became the convenient means of westward movement by pioneers traveling from western Pennsylvania. After reaching the mouth of the Ohio, settlers would travel north on the Mississippi River to St. Louis, Missouri. There, some continued on up the Missouri River, some up the Mississippi, and some further west over land routes. In the early 19th century, pirates, such as Samuel Mason, settled at Cave-In-Rock, Illinois, waylaid travelers on their way down the river, killed them, stole their goods, and scuttled their boats. The folktales of Mike Fink recall the keel boats used for commerce in the early days of European settlement. In 1843 the Ohio River boatmen were the inspiration for Dan Emmett's The Boatman's Dance.
Other boats traveled south on the Mississippi to New Orleans and sometimes beyond to the Gulf of Mexico and other ports in the Americas and Europe. This provided a mush needed route for goods from the west, since the trek east over the Appalachian Mountains was long and arduous. The need for access to the port of New Orleans by settlers in the Ohio Valley led to the Louisiana Purchase in 1803.
Because it is the Southern border of Ohio, Indiana and Illinois, the Ohio River was a part of the border that divided free states and slave states in the years before the American Civil War. The expression "sold down the river" originated as a lament of Kentucky slaves being split apart from their families and sold in Louisville and other Kentucky locations to be shipped via the Ohio River down to New Orleans to be sold yet again to owners of cotton and sugar field plantations. Before and during the Civil War, the Ohio River was called the "River Jordan" by slaves escaping to freedom in the North via the Underground Railroad. As depicted in several novels by Harriet Beecher Stowe and Toni Morrison. More routes, and more escaping slaves made their perilous journey north to freedom across the Ohio River, than anywhere else across the north-south frontier. Today, the Ohio river generally separates Midwestern Great Lakes states from Southern border states.