SH 90's western terminus is a continuation as Utah State Route 46 (SR-46) at the Utah state border, and the eastern terminus is at U.S. Route 550 (US 550) in Montrose.

SH 90 begins in the west at the border with Utah where it becomes Utah State Route 46 which continues westward to meet US 191 about twenty miles (32 km) south of Moab, UT.

From the Utah border the road passes eastward for about 34 miles (55 km) through a very remote area, first along a section of La Sal Creek, then over a pass and though Paradox Valley, where it crosses the Dolores River Bridge near the town of Bedrock.

After leaving the valley, it joins up with SH 141 at Vancorum where this portion of the road ends.

Media related to Colorado State Highway 90 at Wikimedia Commons