Warren County is a county located in the U.S. state of Illinois. As of the most recent data available, the county has a population of approximately 18,735 people, with a population density of about 34.50 persons per square mile.
The county spans a total land area of 543.00 square miles (1,406.00 square kilometers). The administrative center and county seat is Monmouth, which often serves as a hub for local governance and services. The largest city within the county by population is Monmouth.
Geographically, Warren County experiences varied elevations, with its highest point at Monmouth 770 ft and its lowest point at Little York 620 ft. The region operates in the UTC-6.