Cook county's current County Board president is Todd Stroger. The 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 voted only once for a Republican candidate in a Presidential election in the last forty years, when county voters preferred Richard Nixon to George McGovern in 1972.

The Circuit Court of Cook County, which files more than 1.2 million cases every year[3], 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 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 of Cook County, along with over 30 hospitals.

The Cook County Highway Department is responsible for the design and maintenance of roadways in the county. These thoroughfares 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 69,000 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.

In the 1980s, Cook County was ground zero to an extensive FBI investigation named Operation Greylord. Ninety-two officials were indicted, including 17 judges, 48 lawyers, 8 policemen, 10 deputy sheriffs, 8 court officials, and 1 state legislator. Cook County is the fifth largest employer in Chicago.[4]

In March 2008, the Cook County Board increased sales tax one percent, increasing the county sales tax rate from 0.75% to 1.75%. This followed a recent quarter-cent increase in mass transit taxing coming into effect in April. In Chicago, the rate increased to 10.25 percent, the steepest of any major metropolitan area in America[5]. In Evanston, sales tax reached 10 percent and Oak Lawn residents will pay 9.5 percent.[6] On July 22, 2008, the Cook County board voted against Cook County Commissioner's proposal to repeal the tax increase.