In late August of 1958 we moved from Grand Junction Colo. to Washington D.C. (my dad was with USGS and was transfered). We flew Frontier on a DC3 from Grand Jct. to Denver with intermediate stops in Montrose and Gunnison. You definitely flew up the canyons and over the passes. The railroad from Sailda to Gunnison had only been gone a couple of years and the line through the Black Canyon and over Cerro summit just a few more. They were very visible from the air and I spent most of the trip trying to pick them out. I recall that the bridges in the Black Canyon were still there and easy to spot. We flew over Monarch Pass instead of Marshall Pass so I lost sight of the line a little east of Sargents. I did see the mine at Marshall Pass and the switchback at Marysville before the plane headed up the Arkansas toward Trout Creek and South Park.
Stapleton seemed like a huge airport to me compared to Walker Field. There were DC-3s and DC-4s and big 4 engined DC-7s there. You could go out on an observation deck on the roof of the terminal and watch the planes land and take off. Eventually we got on a United DC-7 and flew to Washington.
4 years later (1962) we moved back to Denver but by then DC-8s and Boeing 707s had replaced the the prop planes.
In 64 I finally got a drivers license and started exploring the old railroad grades by car.
John Bush