Springfield is the capital city of the U.S. state of Illinois. Its population was 114,394 at the 2020 United States census, which makes it the state's seventh-most populous city, the second-most populous outside of the Chicago metropolitan area, and the most populous in Central Illinois. Approximately 208,000 residents live in the Springfield metropolitan area, which consists of all of Sangamon and Menard counties. The city lies in a plain near the Sangamon River north of Lake Springfield. Springfield is the county seat of Sangamon County and is located along historic Route 66.