Chicago ( /???k???o?/ (help·info) or /???k???o?/) is the largest city in both Illinois and the Midwest, and the third most populous city in the United States, with over 2.8 million living within the city limits. Its metropolitan area, commonly named "Chicagoland", is the 26th most populous in the world, home to an estimated 9.7 million people spread across the U.S. states of Illinois, Wisconsin, and Indiana. Chicago is primarily located within Cook County, with the exception of a small northwestern portion of the city at O'Hare International Airport that is located within DuPage County.