Monticello is located in Piatt County (of which it is the county seat) about 20 miles northeast of Decatur and 15 miles west-southwest of Champaign along Interstate 72 overlooking the Sangamon River. Clinton Lake is 15 miles to the northwest. The population estimate for 2000 was about 5,200.
The Robert Allerton Park is located here and attracts visitors from around the state as well as around the country.
