- Mattoon is a city located in Coles County, Illinois, United States. It is the county seat of Coles County and has a population of approximately 18,500. Mattoon is known for its historic downtown, which features many preserved buildings from the late 19th and early 20th centuries. The city is also home to Lake Land College, a community college that serves the area. Mattoon has a diverse economy, with industries such as agriculture, manufacturing, and healthcare playing significant roles. The city offers various recreational opportunities, including parks, golf courses, and a regional arts center.