LaSalle County area

Population and density of LaSalle County

The Census Bureau estimates that 107,773 people lived in LaSalle County on July 1, 2025. That ranks #591 of 3,222 county equivalents nationally and #17 of 102 in Illinois. Since the April 1, 2020 estimates base of 109,645, the population has declined by 1,872 (−1.7%), compared with −0.8% for Illinois as a whole.

With 1,135.1 square miles of land, that is 95 people per square mile (37 per km²), placing LaSalle County #1,033 nationally for density and #23 in Illinois. The median county equivalent has 47 people per square mile; the Illinois median is 44. Put another way, there are about 6.7 acres of land per resident.

U.S. Census Bureau, Vintage 2025 population estimates. Estimates are revised each year and are not decennial census counts. Density divides the whole population by the whole county’s land area, so it describes an average, not how settlement is distributed within the county. Population sources and methods.

Cities and towns in LaSalle County

27 incorporated places lie at least partly in LaSalle County. Together they are home to 77,851 people (72.2%); the other 29,922 (27.8%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Ottawa city, with 18,684 residents in the county. Among places with at least 1,000 residents in 2020, North Utica village grew fastest since then (+0.8%).

Population: U.S. Census Bureau Vintage 2025 subcounty estimates, counting only the part of each place inside LaSalle County. Land: 2026 Census Gazetteer, for the whole place even where it extends into other counties. How communities are listed.

Metropolitan area

LaSalle County is a central county of the Ottawa, IL Micropolitan Statistical Area. Its 3 county equivalents have 145,902 residents on 2,164.3 square miles of land; LaSalle County accounts for 52.4% of the land and 73.9% of the residents. By combined land it ranks #73 of 542 micropolitan areas, and #9 by population. It belongs to the Chicago-Naperville, IL-IN-WI Combined Statistical Area.

ZIP codes

29 ZIP Code Tabulation Areas have land in LaSalle County; 26 of them have most of their land inside the county, and the others mainly cover neighboring areas.

6047060518605316053760541605486054960551605526055761301613166132161325613326133461341613426134861350613546135861360613646137061371613726137361377

ZIP Code Tabulation Areas are the Census Bureau’s approximations of USPS ZIP Code service areas, from the 2020 Census relationship files. Lighter codes have less than half of their land in this county. Post-office-box and single-address ZIP Codes have no tabulation area.

Counties bordering LaSalle County

LaSalle County shares a land border with 9 county equivalents. It has more land than every one of them. The largest neighbor is Livingston County (1,043.6 mi²) and the smallest is Putnam County (160.1 mi²). Together with its neighbors, LaSalle County forms a block of 6,216.8 mi² of land, of which it holds 18.3%.

How big is LaSalle County compared with U.S. states?

LaSalle County has more land than 1 of the 50 states. It is about 1.1 times the land area of Rhode Island (1,033.9 mi²), while Delaware, the next larger state, has 1.7 times as much land (1,948.6 mi²). Illinois’s county land could hold about 49 areas the size of LaSalle County.

Another way to picture it: the same land area would fill a square about 33.7 miles (54.2 km) on each side. Real county shapes are rarely square, so this is a scale reference rather than a width or driving distance.

State figures are the sums of each state’s county-equivalent land measurements in the same Census release, so states and counties are compared on the same basis. Published state totals can differ slightly because of rounding. Compare all states · Counties bigger than entire states.

What stands out about LaSalle County?

LaSalle County has more land than 2,672 of the other 3,221 county equivalents in the dataset.

A median is the middle county-equivalent measurement, not the average of the largest and smallest. All three bars use the same linear scale. Very small areas may appear as a thin sliver; the labels retain their values.

Does including water change its rank?

Using land plus water places LaSalle County at #628 nationally by total area, 78 places farther from the top than its land rank. Other county equivalents gain more area when their water measurements are included.

Its water share is 1.1%, compared with a national county-equivalent median of 1.2%. The two percentages are within 0.1 percentage points of each other. This describes the statistical geography’s land/water mix, not flood exposure or developable land.

Closest positions in the national land ranking

These entries sit immediately beside LaSalle County in the national ranking. They can be in different states and are not necessarily geographic neighbors.

Calculated from the same Census release as the area table. Total-area order uses original ALAND + AWATER; water shares and chart labels use published square miles. Calculation details.