Did a little digging and I don't think 'keystone' is directly related to the ski resorts, more of a naming convention by the developers.
Interesting coincidence -
From 2005 https://www.denverpost.com/2005/05/05/cia-set-to-move-unit-to-denver/
Washington – The CIA has plans to relocate the headquarters of its domestic division, which is responsible for operations and recruitment in the United States, from the CIA’s Langley, Va., headquarters to Denver, a move designed to promote innovation, according to U.S. intelligence and law enforcement officials.
About $20 million has been tentatively budgeted to relocate employees of the CIA’s National Resources Division, officials said. A U.S. intelligence official said the planned move, confirmed by three other government officials, was being undertaken “for operational reasons.”
Another interesting image from the Tower road landfill adjacent to the airport (anon source)
Why is the barbed wire tilted inward as if to keep the 'garbage' inside instead of tilting outward to keep intruders out?
Enough smoke here to make me think something's burning...