What is the city code for Denver, Colorado?

The city code for Denver, Colorado, is DEN. This code is specifically designated for Denver International Airport, which is the primary airport serving the Denver metropolitan area. City codes, often referred to as airport codes, are three-letter identifiers used in the aviation industry to simplify the referencing of airports and their locations, which helps in bookings, check-ins, and flight tracking.

DIA is a common abbreviation for Denver International Airport, but it is not the official city code. DFW represents Dallas/Fort Worth International Airport in Texas, while PHL stands for Philadelphia International Airport in Pennsylvania. Therefore, DEN is the accurate and recognized city code for Denver.