Which city code represents Denver, Colorado?

The city code that represents Denver, Colorado, is DEN. This three-letter code is designated by the International Air Transport Association (IATA) and is used by airlines and travel agencies to help identify airports. DEN specifically corresponds to Denver International Airport, which is the primary airport serving the Denver area and one of the busiest airports in the United States.

In contrast, the other options correspond to different cities and airports: DCA represents Ronald Reagan Washington National Airport in Washington, D.C.; DFW is the code for Dallas/Fort Worth International Airport in Texas; and DLH is used for Duluth International Airport in Duluth, Minnesota. Thus, DEN is the correct representation for Denver, ensuring clarity and efficiency in air travel communication.