Population16,835 (2020 Census)
A Historic Square Centers Western Prairie Life
Warren County, IllinoisMonmouth is the county seat and largest city, surrounded by smaller communities and agricultural country. U.S. highways connect the county with neighboring western Illinois centers. This guide brings together a starting point for county information, public services and local connections. Begin with Monmouth, then use the resource links to plan the details of a visit or an everyday errand. Check directly with each provider for current hours, access and service availability before setting out.
Warren County at a Glance
Population16,835 (2020 Census)
County SeatMonmouth
Largest MunicipalityMonmouth
Established1825
ZIP Codes13 ZIP codes wholly or partly within the county (checked October 4, 2026)
Total Area543.0 sq mi (land and water; 2020 Census geography)
Major RoutesU.S. Highway 34; U.S. Highway 67; Illinois Route 94; Illinois Route 116; Illinois Route 135
Area Codes309 / 861 (common local area codes)
Meet Your County Advertisers
Local Connections for Everyday Needs
Explore Jones Septic Services for septic services.
Discover Warren County
Warren County
The county was organized in 1825 and named for Joseph Warren. Henderson County separated from its western portion in 1841, changing its early extent. Today, Monmouth remains the county seat, while Monmouth is its largest municipality. The 2020 Census counted 16,835 residents across the county. Its towns and surrounding countryside offer different ways to understand the same place: through public buildings, transportation routes and the communities that connect them. Local records and historical collections provide a starting point for exploring how those connections changed over time.
Life in Warren County extends beyond a single town center. Monmouth and western Illinois communities are part of the local setting, alongside the routine needs of households, schools and businesses. Use county offices for the services they administer and contact municipal or township offices when a question concerns a specific address. Planning around the actual destination helps make visits, appointments and local errands more practical, especially when travel crosses town or county boundaries.
What Shapes Us
Local Heritage
Established in 1825, Warren County has a history recorded in its communities and public institutions. Start with local collections to explore specific people, buildings and events.
Landscape and Connections
Monmouth and western Illinois communities help distinguish Warren County. Its county seat, Monmouth, provides a useful starting point for understanding how nearby communities connect across the area.
Everyday Community
County and local offices connect residents with practical services. Follow the linked providers for details specific to your destination, address and purpose in Warren County.
Explore the towns, follow the stories, make local connections.
A Look Around
Scenes from Warren County
Places and details that tell a local story.
Radio Monmouth, IL
Hustons Named 2026 Warren County 4-H Hall of Fame Inductees
Read the full story at Radio Monmouth, IL.
Read the Story Oct 19, 2026 • Local news
Around Warren County
Stories from every corner of Warren County.
Hustons Named 2026 Warren County 4-H Hall of Fame Inductees
Read the full story at Radio Monmouth, IL.
Oct 19, 2026 • Local news
Drug Take Back Event Thursday, October 22 at the Warren County Health Department
Read the full story at Radio Monmouth, IL.
Oct 19, 2026 • Local news
Stay Alert: Warren County Sheriff Edwards Reminds Drivers to Watch for Deer
Read the full story at Radio Monmouth, IL.
Oct 19, 2026 • Local news
Sam Brooks & Michelle Johnson with the Warren County YMCA
Read the full story at Radio Monmouth, IL.
Oct 16, 2026 • Local news
Warren County Treasurer Danielle Cox
Read the full story at Radio Monmouth, IL.
Oct 16, 2026 • Local news
Keep These Businesses in Mind
Start with a Direct Conversation
Contact Jones Septic Services directly to ask about current options, availability and the services you need.
County Resources
Find the Right Local Connection
Start with the responsible public agency or service provider. Statewide links are labeled so you can locate the office that serves your address.
Government
County & Local Resources
Supervisor of Assessments
Property assessments, exemptions and assessment office information.
Phone (309) 734-8561
Schools
County & Local Resources
Hospitals and Health
County & Local Resources
St Mary Medical Center
Regional option in Knox County
Address 3333 NORTH SEMINARY, Galesburg
Phone (309) 344-3161
Genesis Medical Center, Aledo
Regional option in Mercer County
Address 409 NW 9TH AVENUE, Aledo
Phone (309) 582-9100
Mc Donough District Hospital
Regional option in McDonough County
Address 525 EAST GRANT STREET, Macomb
Phone (309) 833-4101
Graham Hospital Association
Regional option in Fulton County
Address 210 WEST WALNUT STREET, Canton
Phone (309) 647-5240
Public Safety
County & Local Resources
Illinois State Police
Statewide or federal resource; select the office or service for your address.
Illinois State Police contacts
Find the appropriate State Police contact; call 911 for emergencies.
FBI Internet Crime Complaint Center
Report cyber-enabled crime through the federal complaint portal; emergencies require 911.
Emergency Services
County & Local Resources
Illinois Emergency Management Agency and Office of Homeland Security
Statewide or federal resource; select the office or service for your address.
National Weather Service
Statewide or federal resource; select the office or service for your address.
State Parks
County & Local Resources
Snakeden Hollow State Fish and Wildlife Area
Victoria — regional option in Knox County. Check facilities and access notices.
Argyle Lake State Park
Colchester — regional option in McDonough County. Check facilities and access notices.
Rice Lake State Fish and Wildlife Area
Canton — regional option in Fulton County. Check facilities and access notices.
Nauvoo State Park
Nauvoo — regional option in Hancock County. Check facilities and access notices.
Weinberg-King State Park
Augusta — regional option in Hancock County. Check facilities and access notices.
Trails
County & Local Resources
Argyle Lake State Park
Colchester — regional option in McDonough County. Check trail access and permitted uses.
Horn Field Campus
Macomb — regional option in McDonough County. Check trail access and permitted uses.
Spring Lake Park
Macomb — regional option in McDonough County. Check trail access and permitted uses.
Emiquon National Wildlife Refuge
Lewistown — regional option in Fulton County. Check trail access and permitted uses.
Nauvoo State Park
Nauvoo — regional option in Hancock County. Check trail access and permitted uses.
Utilities
County & Local Resources
Illinois Commerce Commission
Statewide or federal resource; select the office or service for your address.
Illinois 811 — JULIE
Statewide or federal resource; select the office or service for your address.
Illinois energy assistance
Find utility-bill assistance and the local administering agency.
Libraries
County & Local Resources
Warren County Public Library District
Address 62 Public Square Monmouth , IL 61462-1756
Phone 309-734-3166
Henderson County Public Library District
Regional library in Henderson County; check borrowing eligibility
Address 110 Hill Crest Drive Biggsville , IL 61418-9106
Phone 309-627-2450
Bushnell Public Library District
Regional library in McDonough County; check borrowing eligibility
Address 455 North Dean Street Bushnell , IL 61422-1228
Phone 309-772-2060
Colchester District Library
Regional library in McDonough County; check borrowing eligibility
Address 203 Macomb Street Post Office Box 237 Colchester , IL 62326-0237
Phone 309-776-4861
Macomb Public Library District
Regional library in McDonough County; check borrowing eligibility
Address 235 South Lafayette Street Macomb , IL 61455-2231
Phone 309-833-2714
Courts
County & Local Resources
Illinois Courts
Statewide or federal resource; select the office or service for your address.
Illinois Courts — Forms
Statewide or federal resource; select the office or service for your address.
Illinois Court Help
Court-process information and help for people without an attorney.
DMV
County & Local Resources
Transportation
County & Local Resources
Illinois Department of Transportation
Statewide or federal resource; select the office or service for your address.
Getting Around Illinois
Statewide or federal resource; select the office or service for your address.
Illinois public transportation
Find public transportation information and regional agencies.
IDOT transit programs
Transit program information, including rural and intercity services.
Amtrak Illinois services
Find Illinois intercity rail routes and stations; some counties require travel to a regional station.
Postal Services
County & Local Resources
USPS Location Finder
Statewide or federal resource; select the office or service for your address.
USPS ZIP Code Lookup
Statewide or federal resource; select the office or service for your address.
USPS Informed Delivery
Statewide or federal resource; select the office or service for your address.
Veterans
County & Local Resources
Illinois Department of Veterans Affairs
Statewide or federal resource; select the office or service for your address.
VA Facility Locator
Statewide or federal resource; select the office or service for your address.
Veterans Crisis Line
Statewide or federal resource; select the office or service for your address.
Employment
County & Local Resources
IllinoisJobLink — official job-seeker help
Statewide or federal resource; select the office or service for your address.
Illinois Department of Employment Security
Statewide or federal resource; select the office or service for your address.
Illinois workNet
Statewide or federal resource; select the office or service for your address.
Work for Illinois
Statewide or federal resource; select the office or service for your address.
A Useful Starting Point
County facts and practical links for everyday questions.
Questions and Answers
Get to Know Warren County
Find background and service information below, then follow the provider links for current details.
Monmouth is the county seat. Warren County Government provides county office information; check the office destination before traveling.
Monmouth is the largest municipality listed in the county reference. Countywide statistics include other communities and unincorporated areas as well.
The 2020 Census counted 16,835 residents. This is a decennial count, not a current-year population estimate.
Warren County was established in 1825. The county was organized in 1825 and named for Joseph Warren. Henderson County separated from its western portion in 1841, changing its early extent.
The county covers approximately 543.0 sq mi (land and water; 2020 Census geography). This total includes both land and water, rather than land area alone.
Monmouth is the county seat and largest city, surrounded by smaller communities and agricultural country. U.S. highways connect the county with neighboring western Illinois centers.
Discovery Depot Children's Museum is in Galesburg, Knox County. This is a regional option outside Warren County. Check the provider’s current opening times and visitor information before traveling.
Use USPS ZIP Code Lookup with the full street address. A county boundary does not define a single postal delivery area.
Lakeview Nature Center is in Macomb, McDonough County. This is a regional option outside Warren County. Check the provider’s current opening times and visitor information before traveling.
Argyle Lake State Park is in Colchester, McDonough County. This is a regional option outside Warren County. Basic access is the free activity; extras may carry charges. Check the provider’s current opening times and visitor information before traveling.
Begin with the Illinois Department of Veterans Affairs to locate the appropriate service office, or the VA facility locator for federal facilities.
Meet Your County Advertisers
Local Connections for Everyday Needs
Explore Jones Septic Services for septic services.
My Local Guide
Find Something Fun
Explore Local PlacesPlan your next stop around current information from each place.
Kids’ Fun
- Discovery Depot Children's Museum — Galesburg — regional option in Knox County
- Lakeview Nature Center — Macomb — regional option in McDonough County
- Macombopoly — Macomb — regional option in McDonough County
Restaurants
- Iron Spike Brewing Company — Galesburg — regional option in Knox County
- Pizza House – Galesburg — Galesburg — regional option in Knox County
- baked — Galesburg — regional option in Knox County
Shopping & Retail
- The Galesburg Antiques Mall Co. — Galesburg — regional option in Knox County
- Wordsmith Bookshoppe — Galesburg — regional option in Knox County
- Dante & Dory's Pet Emporium — Galesburg — regional option in Knox County
Clothing & Boutiques
- Mother Goosebumps — Galesburg — regional option in Knox County
- Rural Bliss — Carthage — regional option in Hancock County
- Ada Laine Boutique — Princeville — regional option in Peoria County
Outdoor Fun
- Lakeview Nature Center — Macomb — regional option in McDonough County
- Spring Lake Park — Macomb — regional option in McDonough County
- Everly Park — Macomb — regional option in McDonough County
Free Things To Do
- Argyle Lake State Park — Colchester — regional option in McDonough County; basic grounds/trail visit. Rentals, camping, special activities or events may cost extra.
- Snakeden Hollow State Fish and Wildlife Area — Victoria — regional option in Knox County; basic grounds/trail visit. Rentals, camping, special activities or events may cost extra.
- Jubilee College State Park — Brimfield — regional option in Peoria County; basic grounds/trail visit. Rentals, camping, special activities or events may cost extra.
Make Time for Local DiscoveriesChoose Your Next Stop