NG to SG Tennessee Pass

The narrow gauge line was being built in short segments from Leadvile to Glenwood Springs a few years before 1886. Then in 1886 the narrow gauge was extended to Aspen. At the nearly the same time the standard gauge Colorado Midland was built over Hagerman Pass to Aspen. This construction hassened the change to standard gauge for the D&RG.
The earlier route over the top of Tennessee Pass used by the narrow gauge line was abandoned in favor of a new tunnel under Tennessee Pass at about 200 ft lower. The Original tunnel using narrow gauge at Tennessee Pass was built just before standard gauging. In 1890 the Tennessee Pass line was standard gauged and connected the new mainline to Salt Lake City via the Royal Gorge, Tennessee Pass and Soldiers Summit from Denver.
Part of the highway alignment on the west side of the Tennessee Pass is on top of the narrow gauge ROW to near Mitchell Curve. The route on the east side is nearer the mainline route. The route over the pass was switchback and came near the present rest area and memorial to the WW II 10th Mountain Division at the pass.
Get a copy of the books "Rio Grande to the Pacific" and "tracking Ghost Railroads in Colorado". These two books will outline the development of the Rio Grande mainline and provide good maps to follow the ghost routes.
"Rio Grande to the Pacific" is out of print. It may be available in some book dealers on the internet. I think Ghost Railroads is available thru the CRRM.
Dale Brown