Chicago (/ʃɪˈkɑːɡoʊ/ (
listen), locally also /ʃɪˈkɔːɡoʊ/), officially the City of Chicago, is the most populous city in Illinois, as well as the third most populous city in the United States. With an estimated population of 2,716,450 (2017), it is the most populous city in the Midwest. Chicago is the principal city of the Chicago metropolitan area, often referred to as Chicagoland, and the county seat of Cook County, the second most populouscounty in the United States. The metropolitan area, at nearly 10 million people, is the third-largest in the United States.