It travels north–south along the Carbon River between Mount Rainier National Park near Mowich Lake to a junction with SR 410 in Buckley.

[2] Mowich Lake Road is open seasonally from July to October, remaining closed to vehicular traffic during the winter and spring due to weather conditions.

[5] The highway travels northwest along Evans Creek through a section of the Mount Baker–Snoqualmie National Forest, passing several trailheads.

[10] The highway had been preceded by a series of logging roads constructed in the early 20th century by private companies with claims near the national park.

[12][13] The Bureau of Public Roads surveyed the route for a potential connection between the Carbon River and Nisqually entrances to Mount Rainier National Park in the 1920s, but did not fund its construction.