Admission of Illinois as State

Date: December 3, 1818 • Location: Maroa, United States

Illinois becomes the 21st U.S. state.

Illinois is a state in the Midwestern United States. It borders on Lake Michigan to its northeast, the Wabash and Ohio rivers to its south, and the Mississippi River generally to its west. Of the fifty U.S. states, Illinois has the fifth-largest gross domestic product (GDP), the sixth-largest population, and the 25th-most land area. Its capital city is Springfield in the center of the state, and the state's largest city is Chicago, located in northeastern Illinois.