U.S. Route 285

The southern terminus of US 285 is at U.S. 90 in Sanderson. Proceeding northward, it crosses I-10 at Fort Stockton, then meets I-20 at Pecos on its way to New Mexico.

As 285 traverses north on the eastern plains of New Mexico, it passes through Carlsbad, Artesia and then Roswell. In Artesia the route intersects with U.S. Route 82. In Roswell, the route intersects with U.S. Route 70 and U.S. Route 380. The route next heads northwest to Vaughn where it has a brief concurrency with U.S. Route 54 and U.S. Route 60. The route then continues northwest and has a junction with Interstate 40 at Clines Corners.

Clines Corners, at the junction of US-285 and I-40, south of Santa Fe

Heading north out of Clines Corners, the route continues towards the state capital. At the outskirts of Santa Fe, the route becomes concurrent with I-25, U.S. Route 84, and its unsigned parent (U.S. Route 85) for several miles heading west through the foothills of the Sangre De Cristo Mountains to Santa Fe. After exiting I-25, US 285 follows Saint Francis Drive through Santa Fe. The route continues north by northwest to Española and Chamita, where the concurrency with US 84 ends. The route then traverses the Carson National Forest where 285 now makes a long climb up to the Colorado Plateau, passing through Ojo Caliente as it ascends to the San Luis Valley. After crossing US 64, the highway passes through the village of Tres Piedras, New Mexico at the south end of the valley, then proceeds north to the Colorado border.

View of South Park along U.S. Highway 285 looking east toward the Front Range

Heading north from the Colorado border, US 285 passes through the main part of the San Luis Valley, eventually reaching Alamosa. As the highway heads north, it begins to ascend to the northern end of the valley and eventually climbs over Poncha Pass, elevation 9,012 feet (2,747 m), and drops sharply down the other side into the Arkansas River Valley.

The highway brushes Salida and follows the Arkansas River north up the valley, then takes a sharp eastward turn just before the small town of Buena Vista. 285 then climbs over Trout Creek Pass, elevation 9,346 feet (2,849 m), and enters the high-altitude South Park basin.

U.S. 285 entering Saguache County from the north

A few miles north, the highway passes through Fairplay and the historic South Park City site, then reaches its highest elevation: 10,051 feet (3,064 m), at the summit of Red Hill Pass. US 285 then leaves the South Park basin and climbs over Kenosha Pass, elevation 10,001 feet (3,048 m), and skirts the south side of the Mount Evans massif as it descends its way through the foothills range towards Denver.

As the highway leaves the Rocky Mountains and reaches Denver's southwest suburbs, it becomes Hampden Avenue, an important artery in the Denver metro area, then reaches its northern terminus at I-25.

On March 14, 2008, both houses of the Colorado legislature, in a unanimous vote, named the section between Kenosha Pass and C-470 the Ralph Carr Memorial Highway.[2][3]