Winnebago County area

Population and density of Winnebago County

The Census Bureau estimates that 283,674 people lived in Winnebago County on July 1, 2025. That ranks #258 of 3,222 county equivalents nationally and #7 of 102 in Illinois. Since the April 1, 2020 estimates base of 285,351, the population has declined by 1,677 (−0.6%), compared with −0.8% for Illinois as a whole.

With 513 square miles of land, that is 553 people per square mile (213 per km²), placing Winnebago County #316 nationally for density and #6 in Illinois. The median county equivalent has 47 people per square mile; the Illinois median is 44. Put another way, there are about 1.2 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 Winnebago County

11 incorporated places lie at least partly in Winnebago County. Together they are home to 228,865 people (80.7%); the other 54,809 (19.3%) live outside any incorporated place, in unincorporated communities and rural areas.

The largest is Rockford city, with 147,384 residents in the county (the city extends into 1 other county). Among places with at least 1,000 residents in 2020, Loves Park city grew fastest since then (+1.3%).

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

Metropolitan area

Winnebago County is a central county of the Rockford, IL Metropolitan Statistical Area. Its 2 county equivalents have 337,242 residents on 793.8 square miles of land; Winnebago County accounts for 64.6% of the land and 84.1% of the residents. By combined land it ranks #306 of 393 metropolitan areas, and #161 by population. It belongs to the Rockford-Freeport-Rochelle, IL Combined Statistical Area.

ZIP codes

26 ZIP Code Tabulation Areas have land in Winnebago County; 20 of them have most of their land inside the county, and the others mainly cover neighboring areas.

6100861011610166101961020610246104761063610726107361077610796108061084610886110161102611036110461107611086110961111611126111461115

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 Winnebago County

Winnebago County shares a land border with 5 county equivalents, including 2 in Wisconsin. It has more land than 1 of them. The largest neighbor is Ogle County (758.7 mi²) and the smallest is Boone County (280.7 mi²). Together with its neighbors, Winnebago County forms a block of 3,418.9 mi² of land, of which it holds 15%.

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

Winnebago 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 times as much. Illinois’s county land could hold about 108 areas the size of Winnebago County.

Another way to picture it: the same land area would fill a square about 22.7 miles (36.5 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 Winnebago County?

Winnebago County has more land than 1,191 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 Winnebago County at #2,107 nationally by total area, 76 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 1.2%, 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 Winnebago 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.