Warren County is a county in Illinois, United States, on the prairie farmland between the Mississippi and Illinois river valleys. It had a population of 16,835 at the 2020 census and covers 543 square miles (1,406 km2) centred near 40°51′N 90°37′W.
Monmouth is the county seat, and its postal code is 61462. The county has one city, four incorporated villages, and a scatter of unincorporated communities and crossroads settlements. Warren County sits in the Central time zone.
Towns & Villages in Warren County
Warren County has one city — Monmouth, the seat — plus four incorporated villages: Alexis, Kirkwood, Little York, and Roseville. The rest of the entries below are unincorporated communities and rural crossroads, some dating to the county’s earliest settlement in the 1830s. “Unincorp.” covers places with no city or village government of their own; population and ZIP figures are shown only where a source could confirm them.
| Place | Type | Pop. | ZIP |
|---|---|---|---|
| Monmouth | City · seat | — | 61462 |
| Alexis | Village | — | — |
| Kirkwood | Village | — | 61447 |
| Little York | Village | — | 61453 |
| Roseville | Village | — | 61473 |
| Berwick | Unincorp. | — | 61417 |
| Cameron | Unincorp. | — | 61423 |
| Gerlaw | Unincorp. | — | 61435 |
| Smithshire | Unincorp. | — | 61478 |
| Alexis Junction | Unincorp. | — | — |
| Coldbrook | Unincorp. | — | — |
| Eleanor | Unincorp. | — | — |
| Greenbush | Unincorp. | — | — |
| Larchland | Unincorp. | — | — |
| Ormonde | Unincorp. | — | — |
| Phelps | Unincorp. | — | — |
| Ponemah | Unincorp. | — | — |
| Shanghai City | Unincorp. | — | — |
| Shaw | Unincorp. | — | — |
| Surrey | Unincorp. | — | — |
| Swan Creek | Unincorp. | — | — |
| Utah | Unincorp. | — | — |
| Woodvale | Unincorp. | — | — |
| Youngstown | Unincorp. | — | — |
Cameron appeared twice in the county’s old settlement list; the duplicate line has been dropped. Greenbush, near the Henderson County line, is easy to confuse with Green Bush communities elsewhere in Illinois, but this Greenbush is the Warren County hamlet on Illinois Route 116.
ZIP Codes
- 61462 — Monmouth
- 61473 — Roseville
- 61447 — Kirkwood
- 61453 — Little York
- 61423 — Cameron
- 61478 — Smithshire
- 61435 — Gerlaw
- 61417 — Berwick
Smaller unincorporated places such as Alexis Junction, Coldbrook, Eleanor, Larchland, Ormonde, Phelps, Ponemah, Shanghai City, Shaw, Surrey, Swan Creek, Utah, Woodvale, and Youngstown are served by the ZIP code of the nearest post office town rather than one of their own; Alexis, though an incorporated village, is served by a neighboring post office and has no independently confirmed ZIP.
Geography
Warren County lies on rolling glaciated prairie between the Mississippi River to the west and the Illinois River valley to the east, drained by Henderson Creek, Cedar Fork, and Swan Creek. Of its 543 square miles, 542 are land and 0.6 square miles are water. The county borders Mercer County to the north, Knox County to the east, Fulton County to the southeast, McDonough County to the south, and Henderson County to the west.
Warren County shares a border with Fulton County, McDonough County, and Henderson County, all in Illinois. Mercer County and Knox County, also on the county’s borders, do not have a live page on this site yet.
Demographics
Warren County’s population was 16,835 at the 2020 census. Monmouth, the county seat, is by far the largest community; Roseville and Kirkwood are the next-largest incorporated villages. Median household income in the county runs below the Illinois median of $80,306, consistent with the county’s largely agricultural, small-town economic base. Population density is roughly 31 people per square mile.
Economy & Local Life
Corn and soybean farming anchor the Warren County economy, alongside hog and cattle operations spread across its townships. Monmouth is home to Monmouth College, a private liberal arts college founded in 1853, which is one of the county’s largest employers alongside the local school district and hospital. Farm implement dealers, grain elevators, and agricultural supply businesses cluster along U.S. 34 through Monmouth.
History
Warren County was organized in 1825 out of Pike County, before which the land north and west of the Illinois River was unorganized territory attached to Pike County. In 1841 the western portion of the county was split off to form Henderson County, fixing Warren County’s present-day boundary. The county is named for Dr. Joseph Warren, a physician and Massachusetts militia general who was killed at the Battle of Bunker Hill in 1775 and is often remembered as the first American officer to die in the Revolutionary War. The current Warren County courthouse in Monmouth, built of red Portage stone, was completed in 1895 and remains in use.
Getting There
U.S. Highways 34 and 67 cross Warren County, along with Illinois Routes 94, 116, 135, and 164. Monmouth Municipal Airport serves general aviation traffic.
- Galesburg — 17 miles east
- Macomb — 18 miles south
- Burlington, Iowa — 35 miles west
- Peoria — 65 miles southeast
The nearest commercial airport with scheduled service is Quad City International Airport in Moline, roughly 55 miles to the northeast.
Frequently Asked Questions
Where is Warren County, Illinois?
It sits in west-central Illinois, between the Mississippi River and the Illinois River valley, roughly 60 miles east of the Mississippi at the Iowa border.
What is the population of Warren County?
16,835 people, per the 2020 census.
How big is Warren County?
543 square miles (1,406 km2), including 0.6 square miles of water.
What is the county seat of Warren County?
Monmouth is the county seat.
How many towns and villages are in Warren County?
One city (Monmouth) and four incorporated villages (Alexis, Kirkwood, Little York, and Roseville), plus about a dozen smaller unincorporated communities.
What ZIP codes are in Warren County?
Eight confirmed ZIP codes serve the county, led by 61462 (Monmouth), 61473 (Roseville), and 61447 (Kirkwood).
Why is Warren County named Warren?
It honors Dr. Joseph Warren, the Massachusetts militia general killed at the Battle of Bunker Hill in 1775.
More counties in this state: Towns and villages in Illinois.