Monticello is a city and county seat of Piatt County, Illinois, United States. The population was 5,941 at the 2020 census.
Piatt County Courthouse
Monticello Post Office
Bottle of the Syrup Pepsin Company. It reads Monticello, Illinois on the left side.
Buildings on Charter Street
Piatt County is a county in Illinois. According to the 2020 United States Census, it had a population of 16,673. Its county seat is Monticello.
Piatt County Courthouse in Monticello