Decatur /dəˈkeɪtər/ is the largest city and the county seat of Macon County in the U.S. state of Illinois. The city was founded in 1829 and is along the Sangamon River and Lake Decatur in Central Illinois. In 2016, the city's estimated population was 72,706.The city is home of private Millikin University and public Richland Community College. Decatur has vast industrial and agricultural processing production, including the North American headquarters of agricultural conglomerate Archer Daniels Midland, international agribusiness Tate & Lyle's largest corn-processing plant, and the designing and manufacturing facilities for Caterpillar Inc.'s wheel-tractor scrapers, off-highway trucks, and large mining trucks.