On December 3, 1818, Illinois was admitted as the twenty- first state of the Union. Just a few months later on March 26, 1819, Jefferson County was organized by the settlers in the area. This new county …

Jefferson County was organized in 1819, out of parts of White, Edwards and Franklin Counties. It was named in honor of Thomas Jefferson, principal draftsman of the Northwest Ordinance, among other …

Jul 14, 2025 · We anticipate that the sites may be inaccessible for approximately 15 to 45 minutes during the maintenance window. We apologize for any inconvenience this may cause and assure …

Jan 9, 2026 · Mount Vernon, IL – A residential burglary investigation in Jefferson County has led to multiple arrests, the recovery of stolen firearms, and the

Click here to visit the Jefferson County Circuit Clerk website.

Nestled in the southern part of Illinois, Jefferson County is a land that tells stories of pioneers, battles, and the unyielding spirit of the American frontier.

Explore Jefferson County, IL map with detailed charts and insights into its population, demographics, household information, and more.

Map of Jefferson County, Illinois showing cities, highways & important places. Check Where is Jefferson County Located, largest cities, population, areas, and travel info at Whereig.com.

Mount Vernon is the county seat. The Mount Vernon, Illinois micropolitan area is in Jefferson County. It is in the area called “Little Egypt” by the people who live there.

Jefferson county, so called in honor of Thomas Jefferson, the third President of the United States, and the reputed writer and signer of the Declaration of Independence.