It is included in the Colorado Scenic and Historic Byways system and runs through the San Isabel National Forest.

It heads southward through that town before entering the San Isabel National Forest and passing through Cuchara, near the Spanish Peaks Wilderness.

SH 12 heads through Monument Park and turns eastward near Stonewall Gap.

It then passes eastward along the Purgatoire River through Weston, Segundo, Valdez, Cokedale, and Jansen.

The route was established in the 1920s, beginning at Stonewall at SH 111 east to Trinidad and La Junta.