Monroe County is a county in Illinois, United States, on the Mississippi River bluffs directly south of the St. Louis metro area. It had a population of 34,962 at the 2020 census and covers 398 square miles (1,030 km2), of which 385 square miles is land and 13 square miles is water, centred near 38°17′N 90°11′W.
Waterloo is the county seat, and its postal code is 62298. The county has two cities (Waterloo and Columbia), four villages (Fults, Hecker, Maeystown, Valmeyer), and a scatter of small unincorporated communities. Monroe County uses election precincts rather than civil townships as its local subdivision, so there is no township government layer here. The county sits in the Central time zone and is part of the St. Louis, MO–IL combined statistical area.
Towns & Villages in Monroe County
Six places in Monroe County are incorporated; the rest on this list are unincorporated communities, rural crossroads, or historic settlements that never took on city or village government. “CDP” marks a Census-designated place with its own population count; “Unincorp.” covers the smaller hamlets, many of them limestone-bluff river towns dating to early French and German settlement.
| Place | Type | Pop. | ZIP |
|---|---|---|---|
| Waterloo | City · seat | 11,013 | 62298 |
| Columbia | City | 10,999 | 62236 |
| Valmeyer | Village | — | 62295 |
| Hecker | Village | — | 62248 |
| Maeystown | Village | — | 62256 |
| Fults | Village | — | 62244 |
| Renault | Unincorp. | — | 62298 |
| Harrisonville | Unincorp. | — | 62244 |
| Fountain | Unincorp. | — | — |
| Fountain Gap | Unincorp. | — | — |
| Ivy | Unincorp. | — | — |
| Kidd | Unincorp. | — | — |
| Ames | Unincorp. | — | — |
| Burksville | Unincorp. | — | — |
| Chalfin Bridge | Unincorp. | — | — |
| Madonnaville | Unincorp. | — | — |
| Merrimac | Unincorp. | — | — |
| Monroe City | Unincorp. | — | — |
| New Hanover | Unincorp. | — | — |
| Saint Joe | Unincorp. | — | — |
| Tipton | Unincorp. | — | — |
| Wartburg | Unincorp. | — | — |
Two pairs on the old list were duplicate references to the same crossroads rather than separate places — Burksville Station and New Hanover Station are the rail-siding names for Burksville and New Hanover and are folded into those two rows. Kise Crossing, Lemens, Mitchie, and Warnock could not be corroborated against any current gazetteer or the county’s own place-name records and were dropped rather than guessed at.
ZIP Codes
- 62298 — Waterloo (also serves Renault)
- 62236 — Columbia
- 62295 — Valmeyer
- 62248 — Hecker
- 62256 — Maeystown
- 62244 — Fults (also serves Harrisonville)
The smaller unincorporated communities use the ZIP code of their nearest post-office town rather than one of their own.
Geography
Monroe County sits on the Mississippi River bluffs in southwestern Illinois, in a region traditionally known as “Little Egypt.” The Mississippi forms the county’s entire western border, and the bottomland below the bluffs — the American Bottom — floods periodically, which is why the village of Valmeyer relocated to higher ground on the bluff top after the 1993 flood. The bluffs themselves rise sharply from the floodplain and are cut by limestone ravines and sinkholes typical of the region’s karst geology.
Monroe County borders St. Clair County to the northeast and Randolph County to the southeast, both in Illinois. Across the Mississippi River it borders three Missouri counties: Ste. Genevieve County to the south, Jefferson County to the west, and St. Louis County to the northwest.
Demographics
Monroe County had 34,962 residents at the 2020 census. Its two cities, Waterloo (11,013) and Columbia (10,999), together hold roughly two-thirds of the county’s population and sit only a few miles apart along Illinois Route 3. Monroe County has historically run above the Illinois median household income of $80,306, reflecting its role as a commuter suburb for St. Louis; with a total land area of 385 square miles, the county’s overall density is roughly 91 people per square mile, though most residents live in or near its two cities rather than spread evenly across the county.
Economy & Local Life
Monroe County functions largely as a bedroom community for the St. Louis metropolitan area, with many residents commuting north on Illinois Route 3 or across the river into Missouri. Agriculture remains significant away from the two cities — corn, soybeans, and orchard fruit on the bluff-top farmland — and the county is known regionally for its wineries along the Mississippi bluffs. Waterloo and Columbia both maintain their own school districts and small historic downtowns; Maeystown, a 19th-century German stone-building village, is listed on the National Register of Historic Places as a National Historic District.
History
Monroe County was organized in 1816, carved out of Randolph and St. Clair counties as the eighth county created in what was then Illinois Territory. It was named for James Monroe, who was serving as U.S. Secretary of War at the time and would become president the following year. The area was settled early by French colonists moving out from the Kaskaskia settlement, followed by German immigrants who founded Maeystown and other bluff villages in the 1800s. In 1993, the village of Valmeyer was destroyed by Mississippi River flooding and rebuilt on the bluff above its original site — one of the best-known planned town relocations in Illinois history.
Getting There
Illinois Route 3 runs the length of the county along the river bluffs, connecting Waterloo and Columbia to the St. Louis area to the north. U.S. Route 50 crosses the county east–west, and Illinois Routes 156 and 158/159 serve the interior. Interstate 255 touches the county’s northeastern corner near Columbia.
- St. Louis, Missouri — about 20 miles northwest of Waterloo
- Belleville, Illinois — about 15 miles northeast of Waterloo
- Chester, Illinois — about 30 miles south of Waterloo
- Red Bud, Illinois — about 15 miles southeast of Waterloo
St. Louis Lambert International Airport, about 25 miles northwest of Waterloo, is the nearest commercial airport.
Frequently Asked Questions
Where is Monroe County, Illinois?
It is in southwestern Illinois, on the Mississippi River bluffs directly south of St. Louis, Missouri.
What is the population of Monroe County?
34,962 at the 2020 census.
How big is Monroe County?
398 square miles (1,030 km2) total, including 13 square miles of water.
What is the county seat of Monroe County?
Waterloo, which is also the county’s largest city.
How many towns are in Monroe County?
Two cities (Waterloo and Columbia) and four villages (Fults, Hecker, Maeystown, Valmeyer), plus roughly a dozen unincorporated communities.
What ZIP codes are in Monroe County?
62298 (Waterloo), 62236 (Columbia), 62295 (Valmeyer), 62248 (Hecker), 62256 (Maeystown), and 62244 (Fults).
Why did Valmeyer move?
The original village was destroyed in the 1993 Mississippi River flood; residents rebuilt on the bluff top above the floodplain rather than in the same low-lying spot.
More counties in this state: Towns and villages in Illinois.