Missouri played a central role in the westward expansion of the United States, as memorialized by the Gateway Arch. The Pony Express, Oregon Trail, Santa Fe Trail and California Trail all began in Missouri. As a border state, Missouri's role in the American Civil War was complex and there were many conflicts within. After the war, both Greater St. Louis and the Kansas City metropolitan area became centers of industrialization and business. Today the state is divided into 114 counties and the independent city of St. Louis.