Cook County was created on January 15, 1831, by an act of the Illinois State Legislature as the 54th county established in Illinois. Cook County contains 128 municipalities in its region, the most well-known being the City of Chicago. The City of Chicago and the suburban municipalities account for approximately 85% of the County’s 946 square miles, while unincorporated areas make up the remaining 15%.

As mandated by State law, County government has principal responsibility for the protection of persons and property, the provision of public health services, and the maintenance of County highways.