Washington 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 15,148 people, with a population density of about 26.91 persons per square mile.
The county spans a total land area of 563.00 square miles (1,458.00 square kilometers). The administrative center and county seat is Nashville, which often serves as a hub for local governance and services. The largest city within the county by population is Nashville.
Geographically, Washington County experiences varied elevations, with its highest point at Ashley 550 ft and its lowest point at Okawville 440 ft. The region operates in the UTC-6.