State Route 137 is configured as a loop of US-89, with a short southern spur to service the center of Mayfield. It begins in Gunnison as 600 S at its intersection with Main Street (US-89), and travels eastward, turning southeast towards Mayfield as it passes the end of a mountain range. At about the mark, as the route enters Mayfield's town limits, the southern spur splits off and travels south along Main Street for about . The main leg of the route turns north on State Street and continues the north to its terminus at US-89.
