Louisville is the largest city in the Commonwealth of Kentucky and the 29th most-populous city in the United States. Named for King Louis XVI of France, it was founded in 1778 by George Rogers Clark, making it one of the oldest cities west of the Appalachian Mountains. Located beside the Falls of the Ohio, the only major obstruction to river traffic between the upper Ohio River and the Gulf of Mexico, the settlement quickly became one of the busiest ports in the United States.