At Barlow Pass, a gravel road maintained by Snohomish County[4] (closed to motor vehicles) branches from the highway and leads to the former silver mining town of Monte Cristo.

The Mountain Loop Highway starts at the eastern end of SR 92 in Downtown Granite Falls.

[5] The highway goes north away from Granite Falls and turns east at the point where the road meets the South Fork of the Stillaguamish River.

[6] The loop continues and intersects a private road that connects the highway to the Old Monte Cristo Townsite, which is located 4 miles east of Barlow Pass.

At Barlow Pass, the Mountain Loop Highway goes north, and becomes unpaved Forest Route 20 or FR 20.

FR 20 goes northward past Bedal, and it becomes paved again at the new Whitechuck bridge (approximately mile marker 44).

Before the highway was built, primitive and very rough wagon roads connected the Monte Cristo Townsite with the small towns of Darrington and Granite Falls.