Jefferson County, Illinois
Home of Black, Ballard, McDonald, P.C. since 1938
Jefferson County was organized on March 26, 1819, and named for Thomas Jefferson. William Casey donated 20 acres for the county seat, which was first called Mount Pleasant before being renamed Mt. Vernon. The county has a population of approximately 37,000. The 1888 tornado that struck Mt. Vernon destroyed the earlier courthouse.
County Information
- County seat
- Mt. Vernon
- Organized
- March 26, 1819
- Named for
- Thomas Jefferson
- Population
- 37,113 (2020 Census)
- County website
- jeffersoncounty.illinois.gov
- Chamber of Commerce
- southernillinois.com
- Original land
- William Casey donated 20 acres for the county seat
- Original name
- First called Mount Pleasant, then renamed Mt. Vernon
Courts serving Jefferson County
- Judicial circuit
- 2nd Circuit, District: 5
- County seat
- Mount Vernon
- Courthouse
- Jefferson County Courthouse
- Courthouse address
- 100 S 10th St, Mount Vernon, IL 62864
- Court telephone
- (618) 244-8007
- Chief judge
- Lisa Simmons
Divisions and services listed for this court: Disability Information (ADA), e-Filing, Jefferson County Circuit Clerk Website, Online Records, Court Disability Coordinator, E-filing Kiosk, Food (Vending/Other), Free Parking, Internet, Local Rules / Orders, Lockers, Public Transportation, Remote Proceedings.
Work and industry in Jefferson County
- Continental Tires the Americas — 3,496 employees
- Walgreens Distribution Center — 2,138 employees
- Good Samaritan Hospital — 1,484 employees
- National Railway Equipment Company — 376 employees
- Crossroads Community Hospital — 290 employees
- Mount Vernon City Schools, District 80 — 283 employees
- Rend Lake College — 261 employees
- Spero Family Services — 197 employees
- Jefferson County (government) — 178 employees
- Mt. Vernon Township High School — 171 employees
900 business establishments, led by retail trade (146), health care and social assistance (131), other services (123), accommodation and food services (86), construction (62). 2022 County Business Patterns.
Getting to and around Jefferson County
Interstate 57 · Interstate 64 · U.S. Highway 51 · Illinois Route 15 · Illinois Route 37 · Illinois Route 142 · Illinois Route 148
Jefferson County Courthouse · Mount Vernon Township High School
About Jefferson County
- Cedarhurst Craft Fair
Community information compiled from api.census.gov, en.wikipedia.org, illinoiscourts.gov, jeffersoncounty.illinois.gov, southernillinois.com and reviewed 2026-09-10.
Communities in Jefferson County
Legal Services in Jefferson County
Black, Ballard, McDonald, P.C. represents Jefferson County clients in the following practice areas:
Jefferson County sits in Illinois's 2nd Circuit, District: 5, and county matters are filed at the Jefferson County Courthouse.
Contact the Firm
The office is located in Mt. Vernon, Illinois. Contact an attorney to discuss your Jefferson County matter.