Monroe County, Illinois
Monroe County, Illinois, has 34,840 residents (July 2025 estimate). Its county seat is Waterloo. It uses Central Time and covers 385 sq mi (998 km²) of land.
- Resident population, July 2025
- 34,840
- Land area
- 385 sq mi (998 km²)
- County seat or government
- Waterloo
- Time zone
- Central TimeUTC-06:00 in January; UTC-05:00 in July
- Median household income
- $102,880 ± $5,432
- Median home value
- $282,100 ± $13,470
- Median rent, with utilities
- $1,042 ± $61
- Homes lived in by their owners
- 84.7% ± 1.4 points
- County type
- County
- Metro or micro area
- St. Louis, MO-IL metro areaCentral county
- Water area
- 13 sq mi (33.8 km²)
- State
- Illinois
- County code (FIPS)
- 17133
- Coordinates (central point)
- 38.277983, -90.179078
These coordinates mark a central point for the area, not a street address. Income, home value, rent and homes lived in by their owners: U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates, ± margin at 90% confidence; checked on October 13, 2026.
Time zones in Monroe County
| Time zone | Local time and UTC offset | Next clock change |
|---|---|---|
| Central TimeAmerica/Chicago | UTC-06:00 in January; UTC-05:00 in July. Enable JavaScript for the live clock. | Enable JavaScript for upcoming changes. |
Near a time-zone line, check where you are with the time-zone finder. Your phone’s setting can differ.
ZIP Code areas, largest first
- 6229818,208 people
- 6223614,154 people
- 622786,281 people
- 622643,097 people
- 622951,459 people
- 62277940 people
- 62244928 people
- 62248521 people
- 62279112 people
- 6225635 people
10 ZIP Code areas overlap Monroe County. People counts are 2020–2024 estimates for each whole ZIP area. Mailing ZIPs can differ; check an address with USPS ZIP Code Lookup.
Official county information
We don’t have a website for this county yet. The US government’s local-office directory ↗ lists its offices. A geographic lookup cannot determine eligibility, tax liability or a court obligation.
School districts in Monroe County, largest first
- Waterloo Community Unit School District 519,409 people
- Columbia Community Unit School District 413,590 people
- Red Bud Community Unit School District 1327,095 people
- New Athens Community Unit School District 603,764 people
- Valmeyer Community Unit School District 32,259 people
Districts with land in the county; a district can cross county lines. People counts are American Community Survey 2020–2024 5-year estimates. A district boundary doesn’t decide which school a student attends.
Cities, towns and communities, largest first
These areas overlap the mapped boundary; an overlap does not mean that every address belongs to both.
- Waterloo, Illinois (city)11,129 people
- Columbia, Illinois (city)11,127 people
- Dupo, Illinois (village)3,879 people
- Valmeyer, Illinois (village)1,090 people
- Hecker, Illinois (village)521 people
- Maeystown, Illinois (village)65 people
- Fults, Illinois (village)12 people
Bordering areas, nearest first
Distances are straight lines between map points.
- St. Clair County, Illinois19 mi northeast
- Jefferson County, Missouri20 mi west
- Randolph County, Illinois25 mi southeast
- Ste. Genevieve County, Missouri27 mi south
- St. Louis County, Missouri29 mi northwest
Before using this answer on a form
Use a precise point for address-level questions. A device accuracy circle can cross a boundary; confirm tax, voting or jury details with the responsible office.
Find the county where you are now, check its ZIP area, or check the time zone where you are.
Areas that only touch the edge
These areas meet the boundary only along a sliver. Most addresses here are not in them; for an address near the line, check with the county.