U.S. Route 66 (US 66, Route 66) is a former east–west United States Numbered Highway, running from Santa Monica, California to Chicago, Illinois. In Missouri, the highway ran from downtown St. Louis at the Mississippi River to the Kansas state line west of Joplin. The highway was originally Route 14 from St. Louis to Joplin and Route 1F from Joplin to Kansas. It underwent two major realignments (in the St. Louis and Joplin areas) and several lesser realignments in the cities of St. Louis, Springfield, and Joplin. Current highways covering several miles of the former highway include Route 100, Route 366, Route 266, Route 96, and Route 66. Interstate 44 (I-44) approximates much of US 66 between St. Louis and Springfield.