Lake County area

Population and density of Lake County

The Census Bureau estimates that 719,339 people lived in Lake County on July 1, 2025. That ranks #98 of 3,222 county equivalents nationally and #3 of 102 in Illinois. Since the April 1, 2020 estimates base of 714,394, the population has grown by 4,945 (+0.7%), compared with −0.8% for Illinois as a whole.

With 443.7 square miles of land, that is 1,621 people per square mile (626 per km²), placing Lake County #108 nationally for density and #3 in Illinois. The median county equivalent has 47 people per square mile; the Illinois median is 44. Put another way, there are about 0.395 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 Lake County

52 incorporated places lie at least partly in Lake County. Together they are home to 637,862 people (88.7%); the other 81,477 (11.3%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Waukegan city, with 87,940 residents in the county. By land, Barrington Hills village is the largest at 27 mi² across all its counties. Among places with at least 1,000 residents in 2020, Kildeer village grew fastest since then (+14.5%).

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

Metropolitan area

Lake County is a central county of the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area, in the Lake County, IL metropolitan division. Its 13 county equivalents have 9,434,123 residents on 6,923.3 square miles of land; Lake County accounts for 6.4% of the land and 7.6% of the residents. By combined land it ranks #27 of 393 metropolitan areas, and #3 by population. It belongs to the Chicago-Naperville, IL-IN-WI Combined Statistical Area.

ZIP codes

36 ZIP Code Tabulation Areas have land in Lake County; 28 of them have most of their land inside the county, and the others mainly cover neighboring areas.

600026001060013600156002060021600306003160035600406004160042600446004560046600476004860050600516006060061600646006960073600746007560081600836008460085600876008860089600906009660099

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 Lake County

Lake County shares a land border with 3 county equivalents, including 1 in Wisconsin. It has more land than 1 of them. The largest neighbor is Cook County (944.9 mi²) and the smallest is Kenosha County (271.8 mi²). Together with its neighbors, Lake County forms a block of 2,263.9 mi² of land, of which it holds 19.6%.

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

Lake County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 2.3 times as much. Illinois’s county land could hold about 125 areas the size of Lake County.

Another way to picture it: the same land area would fill a square about 21.1 miles (33.9 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 Lake County?

Lake County has more land than 933 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 Lake County at #500 nationally by total area, 1,789 places closer to the top than its land rank. The water assigned to this geography moves it ahead of some county equivalents with more land.

Its water share is 67.6%, compared with a national county-equivalent median of 1.2% — 66.4 percentage points higher. 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 Lake 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.