Decatur is the largest city and the county seat of Macon County in the U.S. state of Illinois, with a population of 70,522 as of the 2020 Census. The city was founded in 1829 and is situated along the Sangamon River and Lake Decatur in Central Illinois. Decatur is the seventeenth-most populous city in Illinois.
The city is home of private Millikin University and public Richland Community College. Decatur has an economy based on industrial and agricultural commodity processing and 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, compactors, large wheel loaders, mining class motor grader, off-highway trucks, and large mining trucks.