Mono Pass to Grinnell Lake and Pioneer Basin
Trip Breakdown
Difficulty Rating: Moderate Days/Nights: 4/3 Distance: 32.34 mi
Elevation Range: 8,763' to 12,046' Total Elevation Gain/Loss: +8,649'/-8,649'
Time of Year: Mid July 2025 Snowpack: 84% (Southern Sierra - Below Average)
The Good: Easy pass; Great trout fishing
The Bad: Bugs along Mono Creek; Steep route up Laurel Creek
Marmot sightings: 0
Largest lake in Pioneer Basin.
A Brief Trail Preview
This Mono Pass (not be confused with the other Mono Pass on the border of Yosemite National Park) begins in Mosquito Flat at the end of Rock Creek Road. The Mono Pass Trail quickly peels off from the Little Lakes Valley Trail from the parking lot.
On this trip, we went over the pass (12,040’) and followed Mono Creek to the Grinnell Lake area and Pioneer Basin.
Route map.
Trail Diary
We got a late start after work (as you can during the height of summer) and hit the trail around 6pm with a short objective for the day - camp at Ruby Lake. The trail from the trailhead to Ruby is an easy and beautiful jaunt, one we often trail run when we stay in the Mammoth area. Ruby Lake was packed when we arrived close to sunset and we struggled to find a cleared spot to camp. We settled in, cooked dinner, and enjoyed our nightcap of choice - little 100ml canned Old Fashioneds called Slow & Low.
The next morning we made breakfast while packing up camp before setting off for the Mono Pass. From Ruby Lake, we climbed a series of sandy switchbacks to Summit Lake. The views to the south of the pass are incredible displays of granite. We made our way down to the larger of the two Trail Lakes, passing a mule train on the way. At the larger Trail Lake there is a handsome stone hut used as a snow survey shelter.
After a few more switchbacks and a crossing of Golden Creek, we leveled off in the valley where Golden Creek converges with Mono Creek. This forested section of trail was dusty and we were swarmed by flies thanks to all the mule dung on the trail. The silver lining was the incredible showing of wildflowers lining the trail in mid July as the trail opened up into a meadow along Mono Creek. We stopped for lunch at a little beach along the creek, sticking our legs in to cool off on this 80+ degree day in the Sierras before our climb up the Laurel Creek drainage towards Grinnell Lake.
The route up the Laurel Creek drainage was very steep, making our final push for the day a slog. But boy were we rewarded when the trail leveled off and opened up to an expansive views of the Silver Divide. We found a campsite perched above the the creek and dropped our packs to go explore Grinnell Lake. There is a loose trail to the lake but we ended up just making our own way. This secluded lake is an oasis, with crystal clear water backed by the dramatic metamorphic rock of Red and White Mountain.
We spent the rest of the evening fly fishing Laurel Creek, brimming with little fingerling brookies. We felt so fortunate to have this little slice of Sierra heaven to ourselves (minus the mosquitoes) that night.
The next morning we hiked back to Mono Creek and made our way towards Pioneer Basin, the most popular destination for those taking Mono Pass into this zone. The flies were flying and we stopped at the same spot along the creek again to refresh ourselves. We were grateful that the hike into Pioneer Basin was much mellower than the route up Laurel Creek. The first lake was already occupied by a group, so we continued hiking to the largest of the lakes in Pioneer Basin. We set up camp, went for a dip in the lake, and did some more fly fishing. Later on we went on a side quest to explore the bowl below Mount Hopkins in hope there was a small lake below the peak but found nothing but rock!
The Great Debate
After our trip, I uploaded a few trout we caught to iNaturalist and sparked a heated debate between trout experts on a possible golden-rainbow hybrid.
We spent our last night watching the sunset from our perch, with Tanner running back and forth to capture the ever shifting colored cloudscape over the valley below. Before bed, we made sure every item of ours was secure due to the basins large population of fearless, food-conditioned Belding’s ground squirrels. Thankfully when we woke up, everything was still intact. We started our hike out early the next morning and made it back to our car at Little Lakes Valley trailhead by lunch.
Before our long drive home, we have a tradition of hopping in a creek or lake to wash off all the dirt and grime of the long weekend. Rock Creek Lake delivered and after we stopped at Rock Creek Lakes Resort for lunch. This is hands down my favorite post-backpacking lunch spot. Can’t beat barbeque, local craft brews, and Pie à la Mode (highly recommend the local apricot pie).
Route elevation info.
