Williamson 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 61,296 people, with a population density of about 144.57 persons per square mile.
The county spans a total land area of 424.00 square miles (1,098.00 square kilometers). The administrative center and county seat is Marion, which often serves as a hub for local governance and services. The largest city within the county by population is Marion.
Geographically, Williamson County experiences varied elevations, with its highest point at Creal Springs 500 ft and its lowest point at Marion 0 ft. The region operates in the UTC-6.