It is operated by the City of Chicago Department of Aviation. Most of O'Hare Airport is in Cook County. However, a section of the southwest part of the airport is in DuPage County. The Cook County portion is located within a section of the city of Chicago contiguously connected to the rest of the city via a narrow strip of land about 200 feet (61 m) wide, running along Foster Ave. from the Des Plaines River to the airport. This land was annexed into the city limits in the 1950s to assure the massive tax revenue associated with the airport being part of the city. The strip is bounded on the north by Rosemont and the south by Schiller Park.