Kendall County is a county in the U.S. state of Illinois, within the Chicago metropolitan area. According to the 2010 census, it has a population of 114,736. Its county seat is Yorkville, and its most populous municipality is Oswego.
According to the U.S. Census Bureau, the county has an area of 322 square miles (830 km), of which 320 square miles (830 km) is land and 2.0 square miles (5.2 km) (0.6%) is water.
Kendall County is a small but rapidly growing county that has the majority of its population in the northeast, and along the Fox River (the only river in the county) which runs through the county’s northwestern section. Many new subdivisions have been constructed in this county, which has produced considerable population growth. Southern Kendall still remains largely agricultural. Kendall County has two primary ranges of low-lying hills formed by what is known as an end moraine. Ransom, the more predominant of the two moraines, runs through the west and north-central part of the county. This moraine has created elevations of over 800 feet (240 m), in contrast to elevations in southern Kendall County that drop to the lower 500 feet (150 m) range. Minooka, the other major end moraine ridge in Kendall County, runs along its entire eastern border with Will County. The two moraines intersect at almost a right angle in the township of Oswego. The county’s only designated state park is Silver Springs State Fish and Wildlife Area.
As of the 2010 United States Census, there were 114,736 people, 38,022 households, and 30,067 families residing in the county. The population density was 358.2 inhabitants per square mile (138.3/km). There were 40,321 housing units at an average density of 125.9 per square mile (48.6/km). The racial makeup of the county was 83.6% white, 5.7% black or African American, 3.0% Asian, 0.3% American Indian, 5.0% from other races, and 2.3% from two or more races. Those of Hispanic or Latino origin made up 15.6% of the population. In terms of ancestry, 28.0% were German, 16.0% were Irish, 9.5% were Polish, 9.4% were Italian, 7.5% were English, and 3.2% were American.
Of the 38,022 households, 47.9% had children under the age of 18 living with them, 65.8% were married couples living together, 9.2% had a female householder with no husband present, 20.9% were non-families, and 16.4% of all households were made up of individuals. The average household size was 3.01 and the average family size was 3.41. The median age was 32.9 years.
The county’s median household income was $79,897 and the median family income was $87,309. Males had a median income of $64,048 versus $42,679 for females. The county’s per capita income was $30,565. About 2.9% of families and 3.9% of the population were below the poverty line, including 4.6% of those under age 18 and 3.4% of those age 65 or over.
It is one of seven out of the 364 largest counties in the United States that has a higher median income for African Americans than White Americans.
Kendall County was listed as the fastest-growing county in the US from 2000 to 2009, experiencing a population growth rate of 110.4% in this period. The reason for this growth is heavy suburbanization from the metropolitan Chicago area.