LaSalle County is a county in Illinois, United States, straddling the Illinois River about 60 miles southwest of Chicago in the Fox Valley and Illinois River Valley region. It had a population of 109,658 at the 2020 census and covers 1,135 square miles (2,940 km2) of land, centred near 41°20′N 88°45′W.
Ottawa is the county seat, and its postal code is 61350. The county holds 8 cities, more than a dozen villages, and dozens of unincorporated communities spread across 37 civil townships. It observes Central time and carries FIPS code 17099.
Towns & Villages in LaSalle County
LaSalle County’s largest places sit along the Illinois River corridor — Ottawa, Peru, LaSalle, Oglesby, and Marseilles — while smaller villages and unincorporated crossroads cover the farmland to the north and south. Two of the county’s cities, Streator and Earlville, straddle a county line and are counted here only for their LaSalle County population and territory. The table below marks incorporated cities and villages by type; CDP denotes a Census Designated Place with no city government, and Unincorp. marks a named crossroads or hamlet with no incorporated government at all.
| Place | Type | Township | Pop. | ZIP |
|---|---|---|---|---|
| Ottawa | City · seat | Ottawa | 18,840 | 61350 |
| Streator | City | Otter Creek | 11,676 | 61364 |
| Peru | City | Peru | 9,835 | 61354 |
| La Salle | City | LaSalle | 9,325 | 61301 |
| Mendota | City | Mendota | 7,235 | 61342 |
| Marseilles | City | Manlius | 4,845 | 61341 |
| Oglesby | City | Utica | 3,451 | 61348 |
| Earlville | City | — | 1,721 | 60518 |
| Seneca | Village | — | 2,144 | 60468 |
| Sheridan | Village | — | 2,335 | 60551 |
| Leland | Village | — | 907 | 60531 |
| North Utica | Village | Utica | 1,032 | 61373 |
| Somonauk | Village | — | 1,668 | 60552 |
| Grand Ridge | Village | Manlius | 558 | 61325 |
| Naplate | Village | Ottawa | 502 | 61350 |
| Cedar Point | Village | Waltham | 416 | 61319 |
| Ransom | Village | — | 442 | 60470 |
| Tonica | Village | Vermillion | 624 | 61370 |
| Rutland | Village | Rutland | 207 | — |
| Troy Grove | Village | Troy Grove | 277 | 61372 |
| Lostant | Village | — | 310 | — |
| Dayton | Unincorp. | Dayton | — | — |
| Deer Park | Unincorp. | Deer Park | — | — |
| Kangley | Unincorp. | — | — | — |
| Wedron | Unincorp. | — | — | — |
| Utica | Village | Utica | 977 | 61373 |
| Dana | Unincorp. | — | — | — |
| Kernan | Unincorp. | — | — | — |
| Norway | Unincorp. | Mission | — | — |
| Jonesville | Unincorp. | — | — | — |
| Leeds | Unincorp. | — | — | — |
| Lowell | Unincorp. | — | — | — |
| Meriden | Unincorp. | Meriden | — | — |
| Milla | Unincorp. | — | — | — |
| Mount Palatine | Unincorp. | — | — | — |
| Peterstown | Unincorp. | — | — | — |
| Prairie Center | Unincorp. | — | — | — |
| Serena | Unincorp. | Serena | — | — |
| Stavanger | Unincorp. | — | — | — |
| Sulphur Springs | Unincorp. | — | — | — |
| Ticona | Unincorp. | — | — | — |
| Triumph | Unincorp. | — | — | — |
| Waltham | Unincorp. | Waltham | — | — |
| Wilsman | Unincorp. | — | — | — |
| Farm Ridge | Unincorp. | Farm Ridge | — | — |
| Garfield | Unincorp. | — | — | — |
| Baker | Unincorp. | — | — | — |
North Utica and Utica are separate villages that sit almost adjacent along the Illinois River near Starved Rock State Park; do not confuse the two on a map. The old county list also carried a handful of duplicated entries (Harding, Serena, Triumph, Wedron each appeared twice) and two entries for defunct public-housing projects with no current population — those duplicates and defunct listings are dropped here; see notes.
Townships
LaSalle County is divided into 37 civil townships, more than almost any other Illinois county. Population figures below are not separately published at the township level in the sources checked for this update, so only the townships whose namesake community is listed above are shown with that link; the remaining townships are open farmland with no incorporated place.
| Township | Pop. (2020) | Main settlements |
|---|---|---|
| Ottawa | — | Ottawa, Naplate |
| Otter Creek | — | Streator (part) |
| Peru | — | Peru |
| LaSalle | — | La Salle |
| Mendota | — | Mendota |
| Manlius | — | Marseilles, Grand Ridge |
| Utica | — | Oglesby, Utica, North Utica |
| Vermillion | — | Tonica |
| Waltham | — | Cedar Point, Waltham |
| Rutland | — | Rutland |
| Troy Grove | — | Troy Grove |
| Dayton | — | Dayton |
| Deer Park | — | Deer Park |
| Mission | — | Norway |
| Meriden | — | Meriden |
| Serena | — | Serena |
| Farm Ridge | — | Farm Ridge |
| Adams, Allen, Brookfield, Bruce, Dimmick, Eagle, Earl, Eden, Fall River, Freedom, Grand Rapids, Groveland, Hope, Northville, Ophir, Osage, Richland, South Ottawa, Wallace | — | rural, no incorporated place |
ZIP Codes
- 61350 — Ottawa (also serves Naplate)
- 61364 — Streator
- 61354 — Peru
- 61301 — La Salle
- 61342 — Mendota
- 61341 — Marseilles
- 61348 — Oglesby
- 60518 — Earlville
- 60468 — Seneca
- 60551 — Sheridan
- 60531 — Leland
- 61373 — North Utica (also serves Utica)
- 60552 — Somonauk
- 61325 — Grand Ridge
- 61319 — Cedar Point
- 60470 — Ransom
- 61370 — Tonica
- 61372 — Troy Grove
Smaller crossroads such as Kangley, Wedron, Dana, and Kernan have no post office of their own and use a neighboring town’s ZIP code.
Geography
LaSalle County sits where the Illinois and Fox rivers meet the Vermilion River, and its terrain runs from the river-carved bluffs and canyons of Starved Rock and Matthiessen State Parks near Utica to flat corn-and-soybean prairie across the rest of the county. The Illinois River bisects the county west to east through Ottawa, Peru, and La Salle, and the Illinois and Michigan Canal historically ran through the same corridor.
LaSalle County borders Lee County to the northwest, DeKalb County to the north, Kendall County to the northeast, Grundy County to the east, Livingston County to the southeast, Marshall County to the south, Putnam County to the southwest, and Bureau County to the west.
Demographics
LaSalle County had 109,658 residents at the 2020 census, spread across a county with no single dominant city; Ottawa (18,840) and Streator (11,676, largely in LaSalle County) are the two largest communities. Median household income runs below the Illinois median of $80,306, typical of a rural-manufacturing county outside the Chicago metro. Population density is about 96 people per square mile.
Economy & Local Life
Manufacturing, agriculture, and energy anchor the county’s economy. The LaSalle County Generating Station, a nuclear plant near Marseilles, is one of the area’s largest employers and taxpayers. Illinois Valley Community College in Oglesby serves the county’s post-secondary students, and OSF Saint Elizabeth Medical Center in Ottawa is the county’s main hospital. Starved Rock State Park near Utica draws well over a million visitors a year and supports a tourism economy of restaurants, wineries, and lodging around the park.
History
LaSalle County was organized on January 15, 1831, formed from parts of Tazewell and Putnam Counties. It is named for the French explorer René-Robert Cavelier, Sieur de La Salle, who passed through the region in the 1680s while building Fort St. Louis on a bluff now within Starved Rock State Park. Ottawa hosted the first of the seven Lincoln–Douglas debates on August 21, 1858, on the courthouse square, an event the city still commemorates.
Getting There
Interstate 80 crosses the county east–west through Ottawa and Peru/La Salle, and Interstate 39 runs north–south through the western part of the county near Peru. U.S. Route 6 and U.S. Route 34 also cross the county.
- Chicago — 75 miles northeast
- Peoria — 45 miles southwest
- Joliet — 40 miles northeast
- Bloomington — 55 miles south
The nearest commercial airport is Illinois Valley Regional Airport in Peru, a general-aviation field; the nearest major airline hub is Chicago’s O’Hare International Airport.
Frequently Asked Questions
Where is LaSalle County?
It is in the north-central part of Illinois, along the Illinois River about 60 miles southwest of Chicago.
What is the population of LaSalle County?
109,658 people at the 2020 census.
How big is LaSalle County?
1,135 square miles (2,940 km2) of land, the largest land area of any Illinois county.
What is the LaSalle County seat?
Ottawa is the county seat.
How many towns and villages are in LaSalle County?
Eight cities and more than a dozen incorporated villages, plus numerous unincorporated communities across the county’s 37 townships.
What ZIP codes are in LaSalle County?
Ottawa is 61350, Peru is 61354, La Salle is 61301, Mendota is 61342, Streator is 61364, and Marseilles is 61341, among others listed above.
Why is it called LaSalle County?
It is named for René-Robert Cavelier, Sieur de La Salle, the French explorer who built Fort St. Louis on the bluff now inside Starved Rock State Park in the 1680s.