Overview
Mosquito Flat, in Inyo National Forest, sits at 10,300 feet, the highest trailhead in the eastern Sierra accessible by passenger car. It's a cornerstone destination in any guide to the best hikes near Los Angeles because the altitude-to-access ratio is unmatched: you begin above 10,000 feet without any climbing to get there. That starting point matters because it means every step of the Mono Pass trail is above the treeline transition zone and into the genuinely alpine. This is not a hike that builds gradually from valley forest to high country: you begin in the high country and climb from there to 12,060 feet, entirely in the zone of granite, talus, scattered whitebark pine, and intense Sierra sky.
Mono Pass is a historic crossing. Native American tribes used this route across the Sierra crest for trade between the eastern and western slopes, moving obsidian, acorns, and other goods through the high country. During the gold rush era, miners used the pass to access diggings on both sides of the Sierra. Those human uses ended as the country was incorporated into the national forest system, and now the pass is a waypoint on the John Muir Trail, which crosses it on its route from Yosemite south toward the Muir Trail Ranch and beyond.
The approach from Mosquito Flat climbs through the Rock Creek drainage past a series of high lakes: Ruby Lake, Summit Lake, and the small tarns that sit in the granite bowls below the pass. Each lake is a destination in its own right, and the cumulative effect of walking through this chain of high-altitude water and granite is what makes the trail memorable. At the pass itself, the view opens west into the Yosemite high country, with the peaks of the main Sierra crest running in both directions.
At 8.4 miles round trip with 1,800 feet of gain starting at 10,300 feet, this trail is rated moderate-hard primarily because of altitude rather than technical difficulty. Fit hikers acclimatized to elevation will find the grade manageable. Those who drove up from sea level the morning of the hike will find the altitude a significant obstacle. Spend a night in Bishop or at a Rock Creek campsite before attempting Mono Pass if you're coming from low elevation.
The Route
Miles 0 to 1.5: The trail begins at Mosquito Flat and immediately enters the John Muir Wilderness, heading southwest up the Rock Creek drainage. The first section crosses open granite slabs and meadow, with the creek to the south and the surrounding peaks already visible in full from the trailhead. Ruby Lake sits at the 1.5-mile mark at around 11,100 feet: a deep blue lake in a granite bowl that is a worthwhile destination for hikers who want a shorter day (3 miles round trip, about 800 feet of gain). The lake sits below the flanking ridges, with clear views of the Sierra crest above it.
Miles 1.5 to 2.5: Past Ruby Lake, the trail continues southwest and upward through progressively more open terrain. Summit Lake appears at about 2.5 miles, sitting at roughly 11,300 feet. The lake is smaller than Ruby Lake but sits in a more dramatic setting, with the headwall below the pass rising directly above it. By this point the trail is above any significant vegetation other than low alpine willow and scattered whitebark pine. The route is mostly over granite slabs and packed trail surface, with a few rocky sections.
Miles 2.5 to 4.2: The final push to the pass gains most of the remaining elevation in a sustained climb up the headwall above Summit Lake. The grade is steep but the distance is short. The trail switchbacks through talus and granite bench terrain, and the footing requires attention. Snow can persist on this headwall into August in heavy snow years. The John Muir Trail joins from the north before the final approach to the pass, and the junction is marked. At Mono Pass (12,060 feet), the Sierra crest opens in both directions and the view west into the Yosemite high country appears: a rolling landscape of granite domes, tarn lakes, and glacially carved valleys extending toward the headwaters of the San Joaquin River. Return the same way.
When to Visit
July: Mosquito Flat Trailhead is typically accessible by late June, and the lower trail to Ruby Lake is usually snow-free by early July. The headwall above Summit Lake and the pass itself may hold snow into mid-July. An ice axe is useful on the upper headwall in early July if significant snow remains. Check conditions with the White Mountain Ranger District before a July visit.
Late July through August: The best conditions for most hikers. The full trail is typically clear of snow by late July, the lakes are at their most vivid blue, and the days are long. Afternoon thunderstorms over the Sierra crest are a regular feature in July and August. The pass is fully exposed, at 12,060 feet, with no shelter. Start early and target the pass before noon.
September: A genuinely excellent month for this trail. Crowds are dramatically thinner after Labor Day. The high country is dry, the rock is clean, and the light is the best of any season. Snow can arrive at the pass by mid-September in some years. Bring layers and check forecasts.
October: Rock Creek Road typically closes in October, and snow can make the upper trail dangerous well before the road closes. Treat October visits as weather-dependent.
Practical Details
Parking: Paved lot at Mosquito Flat Trailhead. Inyo National Forest day-use fee ($5) or America the Beautiful Pass required. The lot holds approximately 40 cars but can fill by 7 AM on summer weekends. Arrive early or plan for overflow parking along Rock Creek Road.
Permits: No permit required for day hikes. Overnight trips in the John Muir Wilderness require a permit with a daily quota. Mosquito Flat has one of the most competitive permit quotas in the eastern Sierra; book on Recreation.gov six months in advance for summer weekend overnights.
Dogs: Allowed on leash. The high altitude and rocky terrain above Summit Lake are demanding for dogs. Watch for altitude sickness (lethargy, unsteady gait) and have a plan to turn around if your dog shows distress. The talus section below the pass can be rough on paws.
Water: Ruby Lake and Summit Lake are water sources; carry a filter. No reliable water above Summit Lake on the final push to the pass. Carry at least 2 liters from the trailhead.
Altitude: The trailhead is at 10,300 feet. The pass is at 12,060 feet. Altitude-related symptoms (headache, nausea, reduced energy) are common for hikers who haven't acclimatized. Spend at least one night above 7,000 feet before this hike. If you feel significantly unwell above 11,000 feet, descend.
Facilities: Vault toilet at Mosquito Flat. No facilities on the trail.
Getting There
From Bishop, take US-395 North for about 15 miles to the Tom's Place junction (Crowley Lake Drive). Turn left (west) onto Rock Creek Road and follow it all the way to its end at Mosquito Flat Trailhead, approximately 11 miles from US-395. The drive from Bishop takes about 30 minutes.
From Mammoth Lakes, take US-395 South for roughly 20 miles to the Tom's Place junction. Turn right onto Rock Creek Road and follow it to the end. Total drive from Mammoth is about 35 minutes.
Note that Mosquito Flat is at the end of Rock Creek Road, past Rock Creek Lake (the Hilton Lakes trailhead). Both trailheads use the same access road. Mosquito Flat is about 1 mile further up the road from Rock Creek Lake.
The Bottom Line
Mono Pass combines the most accessible high-altitude starting point in the eastern Sierra with a genuine alpine destination at 12,060 feet. The historic route, the chain of lakes on the approach, and the view into the Yosemite high country from the pass make this one of the most rewarding moderate-hard day hikes in Inyo National Forest.
The Rock Creek corridor that hosts both Mono Pass (Mosquito Flat) and Hilton Lakes (Rock Creek Lake) gives you two excellent hikes on the same access road, at different difficulty levels. For similar high-pass experiences elsewhere in Inyo, Kearsarge Pass near Independence and Bishop Pass from South Lake follow the same lake-chain-to-pass structure with their own distinct granite basins. If you're visiting Mammoth Lakes, Duck Pass is another strong option at 10,797 feet. For an entirely different kind of Inyo day, the Methuselah Trail in the White Mountains crosses 4,800-year-old bristlecone pines at 10,100 feet on the opposite side of the Owens Valley.