Cook County is a county located in the U.S. state of Illinois. As of 2010, the population was 5,194,675, making it the second largest county by population in the United States (after Los Angeles County, California). The county seat is Chicago, the principal city of its metropolitan area, Chicagoland; Chicago makes up about 54% of the population of the county, the rest being provided by various suburbs, and Cook county itself makes up 43.3% of the state population as of 2010. Cook County is the 19th largest government in the United States. Cook County has by far more Democratic Party members than any other Illinois county and is one of the most Democratic counties in the United States. It has only voted once for a Republican candidate in a Presidential Election in the last forty years, in 1972, when Cook county voters preferred Nixon to McGovern by 53.4% to 46%.
Cook County's current County Board President is Toni Preckwinkle. She was elected on November 2, 2010.
Cook County was created on January 15, 1831 by an act of the Illinois State Legislature. It was the 54th county established in Illinois and was named after Daniel Pope Cook, one of the earliest and youngest statesmen in Illinois history who served as the first U.S. representative from Illinois and the first Attorney General of the State of Illinois.
As mandated by State law, Cook County government has principal responsibility for the protection of persons and property, the provision for public health services and the maintenance of County highways.
The obligation to protect persons and property, commonly called public safety, is fulfilled by the provision of County judicial and law enforcement services: the Circuit Court of Cook County, which is the largest unified court system in the world - disposing over 6 million cases in 1990 alone, the Cook County Department of Corrections, which is the largest single-site jail in the nation and the Cook County Juvenile Detention Center, the first juvenile center in the nation and one of the largest in the nation, are solely the responsibility of Cook County government. The Cook County Law Library is the second largest County law library in the nation.
The obligation to provide public health services is fulfilled by the provision of comprehensive medical services to the citizens of the County, regardless of their ability to pay. The Bureau of Health Services administers the county's public health services and is the second largest public health system in the nation. Three hospitals are part of this system: John H. Stroger, Jr. Hospital of Cook County, Provident Hospital and Oak Forest Hospital, along with over 30 outpatient clinics.
The Cook County Highway Department is responsible for the design and maintenance of over 578 miles of roadways in the county. These thouroughfares are mostly composed of major and minor arterials, with a few local roads. Although the Highway Department was instrumental in designing many of the expressways in the county, today they are under the jurisdiction of the state.
The Forest Preserve District, organized in 1915, is a separate, independent taxing body, but the Cook County Board of Commissioners also acts as the Forest Preserve District Board of Commissioners. The District is a belt of 68,000 acres (275 km²) of forest reservations surrounding the City of Chicago. The Brookfield Zoo (managed by the Chicago Zoological Society) and the Chicago Botanic Garden (managed by the Chicago Horticultural Society) are located in the forest preserves. The Brookfield Zoo is a zoo located in the Chicago suburb of Brookfield, Illinois.
According to the U.S. Census Bureau, the county has a total area of 1,634.33 miles. 945.33 miles is land and 689 miles (42.16%) is water, most of it in Lake Michigan.
As of the census of 2010, there were 5,194,675 people and 1,936,481 households residing in the county. The population density was 5,495.1 persons per square mile. There were 2,180,359 housing units at an average density of 2,306/mile. The racial makeup of the county was 55.4% White, 24.8% Black or African American, 0.4% Native American, 6.2% Asian, 0.04% Pacific Islander, 9.88% from other races, and 2.5% from two or more races. 24.0% of the population were Hispanic or Latino origin.
There were 1,936,481 households out of which 30.9% had children under the age of 18 living with them, 44.0% were married couples living together, 15.6% had a female householder with no husband present, and 35.7% were non-families. 29.4% of all households were made up of individuals and 9.3% had someone living alone who was 65 years of age or older. The average household size was 2.68 and the average family size was 3.38.
In the county the population was spread out with 23.7% under the age of 18, 9.9% from 18 to 24, 31.7% from 25 to 44, 20.7% from 45 to 64, and 11.9% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 93.9 males. For every 100 females age 18 and over, there were 90.5 males.
The median income for a household in the county was $53,942. The per capita income for the county was $29,335. About 15.3% of the population were below the poverty line.