Decatur is the largest city and the county seat of Macon County in the U.S. state

U.S. state

A U.S. state is any one of the 50 federated states of the United States of America that share sovereignty with the federal government. Because of this shared sovereignty, an American is a citizen both of the federal entity and of his or her state of domicile. Four states use the official title of...

 of Illinois

Illinois

Illinois is the fifth-most populous state of the United States of America, and is often noted for being a microcosm of the entire country. With Chicago in the northeast, small industrial cities and great agricultural productivity in central and northern Illinois, and natural resources like coal,...

. The city, sometimes called "the Soybean Capital of the World", was founded in 1823 and is located along the Sangamon River

Sangamon River

The Sangamon River is a principal tributary of the Illinois River, approximately long, in central Illinois in the United States. It drains a mostly rural agricultural area between Peoria and Springfield...

 and Lake Decatur

Lake Decatur

Lake Decatur is a reservoir located in the city of Decatur, Illinois, east of downtown. The city and lake both share the name of U.S. Navy Commodore Stephen Decatur. The lake is above sea level. Lake Decatur has a watershed of 925 square miles spanning 7 counties...

 in Central Illinois. In 2000 the city population was 81,500, and 76,122 in 2010. Decatur is the sixth-most populous city in Illinois, outside of the Chicago Metropolitan Area.