[3] Highway 37 begins at an intersection with U.S. Route 2 in downtown Libby, Montana, and heads northeast.

The road follows the river upstream into a narrow, tightly winding canyon, running parallel to the railroad on the opposite bank.

It suddenly turns south near the former vermiculite mine[6] and passes by its former processing plant site.

[5][7] Soon, the road turns east again, then crosses the Kootenai once more and abruptly heads north, parting ways with the now southbound railroad.

It bypasses the town to its south as the road turns east, passing over a former railroad alignment a few miles later, before turning east one last time amidst farmland to terminate at U.S. Route 93, at the northern end of Eureka.