Stapleton International Airport (IATA: DEN, ICAO: KDEN, FAA LID: DEN) was a major airport in the western United States, and the primary airport of Denver, Colorado. It opened on October 17, 1929, and was replaced by Denver International Airport in 1995.
It was a hub for Continental Airlines, the original Frontier Airlines, People Express, United Airlines, and Western Airlines. Other airlines with smaller operations at Stapleton included Aspen Airways, today’s Frontier Airlines, and Rocky Mountain Airways, all three being based in Denver at the time.