What is the ICAO code for Chicago O'Hare, IL?

The ICAO code for Chicago O'Hare International Airport is KORD. The ICAO (International Civil Aviation Organization) codes are four-letter alphanumeric codes that are used globally to identify airports. These codes typically start with a letter that represents the region or country. In the case of Chicago O'Hare, the 'K' signifies that the airport is located in the United States, while 'ORD' is derived from the airport's former name, Orchard Field.

The other choices presented do not represent the correct ICAO code for Chicago O'Hare. KCHI could be confused with a different airport, as it suggests Chicago Midway but is not the ICAO code for either of the main Chicago airports. ORD is actually the IATA code for the airport and does not fit the ICAO format. KOOH does not correspond to any known airport and does not follow the established naming conventions for ICAO codes in the U.S. Thus, KORD is the only choice that accurately identifies Chicago O'Hare's ICAO code.