SH 149 begins in the south at its junction with US 160 at South Fork. From there the road winds its way generally northward through the San Juan Mountains. The first portion of the road parallels the upper Rio Grande as it passes through Rio Grande National Forest. SH 149 winds through the mountains for before coming to the historic mining town of Creede. From there the road continues its climb into the mountains and eventually turns away from the Rio Grande to cross the Continental Divide at Spring Creek Pass at an elevation of . At this point the road passes into Gunnison National Forest and, after a brief descent, begins an even higher climb to Slumgullion Pass elevated . From there, the highway descends and crosses the Slumgullion Earthflow before it drops to the town of Lake City, where it begins to parallel Lake Fork, a tributary of the Gunnison River. SH 149 follows Lake Fork down out of the mountains and eventually turns away to the east passing just north of Powderhorn where the road again turns northward. After skirting the southern edge of Curecanti National Recreation Area, the highway crosses the Gunnison River and finally reaches its northern terminus at US 50 approximately nine miles west of Gunnison. There are no major junctions along its entire length.