Chicago (ⁱ/ʃɪˈkɑːɡoʊ/ or /ʃɪˈkɔːɡoʊ/) is the largest city in the U.S. state of Illinois and the third most populous city in the United States, with around 2.7 million residents. Its metropolitan area, sometimes called "Chicagoland," is the third largest in the United States, with an estimated 9.8 million people in the states of Illinois, Wisconsin and Indiana. Chicago is the county seat of Cook County, the second most populous county in the United States.