Utah’s Uinta Mountains are a unique range. One of the only mountain ranges in the continental United States that run east to west, the Uintas include dozens of peaks over 12,000 feet of elevation. One of the most accessible of these peaks is Mount Agassiz (12,428 feet), named after the well-known American naturalist, Louis Agassiz. While the mountain can be climbed via several routes, the most popular, and likely easiest, begins in Naturalist Basin. Roughly 14 miles round trip, this route starts at the Highline Trailhead, loops around the mountain to the south, and climbs the east ridge from Blue Lake. The hike can be done in one long day, or you can camp in Naturalist Basin and spend two shorter, more leisurely days.
Start by heading into Naturalist Basin from the Highline Trail/Hayden Pass Trailhead. From the south end of the parking area the trail descends to the south to a junction with the trail to Mirror Lake at about three-quarters of a mile. Stay left to continue on the Highline Trail heading southeast. The trail arrives at a junction with the Packard Lake Trail about 3 miles from the trailhead. Stay left to continue on the Highline Trail for another 1.2 miles to reach an intersection with the trail to Naturalist Basin. At the fork, leave the Highline Trail and stay left and north to reach Naturalist Basin. Upon arriving at the open meadow where the trail forks, go left to pass Morat Lakes and reach Blue Lake (10,945), about 6 miles from the trailhead.
Blue Lake is a good spot to camp if you’re doing this route as an overnight. You are right at the timberline, and the terrain around you is open and rocky, a stark contrast with the dense spruce forests you passed through on the hike in. The route ascends the rocky slopes directly to the north, reaching the crest of the ridge at about 11,500 feet. The barren moonscape of the ridge above lacks any reference for scale, so the distance may be deceptive, but you’ve got about 1,000 feet of climbing ahead at this point. Follow the east ridge up to the top. There are some loose rocks on this route, including some surprisingly large boulders that shift under weight, so step carefully.
At the summit, take in the expansive views of Naturalist Basin to the east and Middle Basin to the north. Other nearby peaks include Hayden Peak (12,479 feet) to the northwest and Spread Eagle Peak (12,540 feet) to the east. Mount Agassiz is best climbed in summer, when the upper slopes are snow-free. A winter ascent would have to contend with avalanche danger and a very long approach because the Mirror Lake Highway is closed in winter.