A highway, it was argued, built on Marshall would have the added advantage of not having to cross the railroad switchbacks that were on the eastern slope of Monarch Pass, part of the spur line that served the limestone quarry.In fact, I believe the only thing Monarch Pass had going for it as the route of US 50 was...it's name. Monarch was known as Monarch-Agate Pass to the state highway department and rumor has it that Charles D. Vail, the State Engineer, planned to give Monarch-Agate a much more simple and modest name...Vail Pass. Alas, it was not to be, likely because local residents objected. Instead, a crossing west of Dillon would be given that "honor." Highway 50 still went over Monarch, but without Vail's name attached to it.
Marshall Pass lost its rails in 1955; Monarch in the early 1980s. Marshall has a lonely Forest Service road built on much of the old narrow gauge roadbed while Monarch retains US 50. Had the highway been built over Marshall, it's possible the narrow gauge grade would have been obliterated by an ever-widening highway in the 60s and 70s.
Today, it's still possible to examine much of the Marshall Pass line as it travels between Poncha Springs and Gunnison. It's a quiet, peaceful place, and although no structures still exist on the summit, it's still possible to imagine the whistles of engines working their way to the summit.