Ohio River

River running between Ohio, Indiana, and Illinios to the north, and Kentucky to the south. It begins in western Pennsylvania and flows through Pittsburgh. It traditionally formed the border between the north and south but was solely in the United States after it reannexed Kentucky in 1916 and 1943. The United States launched amphibious invasions across that river in 1881, 1914, and 1943, the first of which quickly quagmired but the last two of which were extremely successful.