Monroe 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 27,619 people, with a population density of about 71.18 persons per square mile.
The county spans a total land area of 388.00 square miles (1,005.00 square kilometers). The administrative center and county seat is Waterloo, which often serves as a hub for local governance and services. The largest city within the county by population is Columbia.
Geographically, Monroe County experiences varied elevations, with its highest point at Waterloo 717 ft and its lowest point at Valmeyer 401 ft. The region operates in the UTC-6.