One of the steepest standard 14er routes in the Sawatch, made short by a 4WD road that climbs most of the mountain's flank.
From Nathrop, follow Mount Princeton Road (County Road 162) toward the radio towers; the road is 4WD-recommended above a certain point and parking at the upper areas is limited, so arriving early matters. Vehicles without sufficient clearance should plan to park at the lower 2WD trailhead near the end of County Road 322 instead, which adds roughly 6.75 miles and 2,100 feet of gain each way. From the upper 4WD parking near the radio towers (about 10,800 feet), continue on the road for roughly 1.6 miles and 1,000 feet of gain until the marked Mount Princeton Trail leaves the road on the right, just below treeline — it's easy to walk past this junction. From there, a steep 1.25-mile trail climbs rocky slopes to Princeton's summit ridge and the top at 14,197 feet; snow can linger on this upper section later into the season than on most of the route.
Reverse the route. Trekking poles are worth carrying given the sustained steep grade on the descent.