Denver First-They pretty much flew to all the big cities non-stop like Seattle, Newark, Dallas, Washington, Philadelphia, etc. and even Honolulu and London with 747's and DC-10's. When they bought Frontier, they ended up with more routes to smaller cities like Boise (remember flight 1713), ands even Cody Wyoming. They had Continental Express going to small cities in Wyoming, Colorado, and Nebraska. They had two big hangars there and when they bought Frontier I am not sure if they took Frontier's hangar or not, but it was impressive in size.
Now LAX-I only go back to the early eighties because that's when my mind officially was old enough to recall, but they flew nonstop to Hawaii, Fiji, Denver, Houston, Washington Dulles, San Jose, San Antonio, El Paso, Ontario, Albuquerque, and Newark. I got this from old timetables. They also had a hangar in LAX.
Both operations closed because they weren't profitable and I think the new Denver airport was the final blow.
A side note-Texas International was actually stronger at dallas then it was in Houston.