Jersey 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 21,668 people, with a population density of about 58.72 persons per square mile.
The county spans a total land area of 369.00 square miles (956.00 square kilometers). The administrative center and county seat is Jerseyville, which often serves as a hub for local governance and services. The largest city within the county by population is Jerseyville.
Geographically, Jersey County experiences varied elevations, with its highest point at Fieldon 700 ft and its lowest point at Grafton 435 ft. The region operates in the UTC-6.