Monmouth is the county seat of Warren County in the U.S. state of Illinois. It is the home of Monmouth College and contains Monmouth Park, Harmon Park, North Park, Warfield Park, West Park, South Park, Garwood Park, Buster White Park and the Citizens Lake & Campground. It is the host of the Prime Beef festival [], held annually the week after Labor Day. Monmouth apartments for rent comparison page shows most up to date rent information on Monmouth apartments and houses. Rent information is obtained from multiple rental sources but we cannot guarantee their accuracy.