Kendall County area

Population and density of Kendall County

The Census Bureau estimates that 145,470 people lived in Kendall County on July 1, 2025. That ranks #474 of 3,222 county equivalents nationally and #14 of 102 in Illinois. Since the April 1, 2020 estimates base of 131,876, the population has grown by 13,594 (+10.3%), compared with −0.8% for Illinois as a whole.

With 320.2 square miles of land, that is 454 people per square mile (175 per km²), placing Kendall County #371 nationally for density and #8 in Illinois. The median county equivalent has 47 people per square mile; the Illinois median is 44. Put another way, there are about 1.4 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 Kendall County

15 incorporated places lie at least partly in Kendall County. Together they are home to 119,506 people (82.2%); the other 25,964 (17.8%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Oswego village, with 39,948 residents in the county (the city extends into 1 other county). The county seat, Yorkville city, has 26,730 residents. By land, Joliet city is the largest at 66.3 mi² across all its counties. Among places with at least 1,000 residents in 2020, Yorkville city grew fastest since then (+23.6%).

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

Metropolitan area

Kendall County is a central county of the Chicago-Naperville-Elgin, IL-IN Metropolitan Statistical Area, in the Elgin, IL metropolitan division. Its 13 county equivalents have 9,434,123 residents on 6,923.3 square miles of land; Kendall County accounts for 4.6% of the land and 1.5% 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

19 ZIP Code Tabulation Areas have land in Kendall County; 8 of them have most of their land inside the county, and the others mainly cover neighboring areas.

60431604476045060503605046050660512605366053760538605416054360544605456054860554605606058560586

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 Kendall County

Kendall County shares a land border with 5 county equivalents. Each of them has more land than Kendall County. The largest neighbor is LaSalle County (1,135.1 mi²) and the smallest is Grundy County (418.1 mi²). Together with its neighbors, Kendall County forms a block of 3,860.1 mi² of land, of which it holds 8.3%.

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

Kendall County has less land than any of the 50 states. Rhode Island, the smallest state by land area, has 1,033.9 mi², about 3.2 times as much. Illinois’s county land could hold about 173 areas the size of Kendall County.

Another way to picture it: the same land area would fill a square about 17.9 miles (28.8 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 Kendall County?

Kendall County has more land than 461 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 Kendall County at #2,801 nationally by total area, 40 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 0.6%, compared with a national county-equivalent median of 1.2% — 0.6 percentage points lower. 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 Kendall 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.