The Mono Pass Trail is a very popular run. Some of these runners will stop at Ruby Lake. Most of those who continue will go over the pass to Summit Lake or even continue another 0.5 miles to a viewpoint that overlooks the Mono Creek canyon and upper lake basins. Most runners making overnight trips across Mono Pass will stop at the 4th Recess or Pioneer Basin. It is a little over 7 miles to the Fourth Recess Lake and nearly 8 miles to the lowest Pioneer Basin lake. For those who can afford it, the Rock Creek Pack Station is quite busy, carrying food and gear to destinations beyond the pass.
On the west side of the Sierras, between Tioga Pass Road and Bishop, the name, "Mono Pass" is used for 2 different and unrelated passes and trailheads. The other Mono Pass Trail starts from Dana Meadows in Yosemite and crosses over a Mono Pass that leads towards Parker Pass or Bloody Canyon. Again, the "Mono Pass" name is the same, but it is a different, unrelated trail.
There is a walk-in campground at Mosquito Flats that is only available for those with a wilderness permit for the next day.
I saw many dogs, but dogs-on-a-leash were a rare breed.
The Mono Pass Trail starts in Little Lakes Valley at Mosquito Flats, which at 10,270 feet is the highest trailhead in the Sierras. It follows the Parker Pass Trail
for about 0.5 miles and then branches off to the right. For the next 1.4 miles, the trail climbs the side of the canyon, alternating between moderately steep climbs and mostly level sections as it traverses a rocky shelves a few hundred feet above Little Lakes Valley. Views from the shelves are especially scenic with the afternoon sun shining up the valley. Several people that I passed spontaneously commented on the beautiful wildflowers.
At 1.9 miles, there is an easy 0.25-mile lateral trail to the beautiful Ruby Lake. Good campsites can be found near the lakes outlet. I recommend one on the rocks, 30-40 feet above the trail.
From the lateral, the trail begins a steady, moderately steep climb up to the pass. This is best done as a morning run, because there is no water and very little shade between here and Summit Lake. In spite of the altitude, it can be hot in the bright sun. For the first mile, the trail switchbacks up the rocky slopes. There are extraordinary views of Ruby Lake and the steep granite cliffs of the surrounding 13,000-foot mountains, including Mt. Abbot at 13,704 feet. The trail then swings into a narrow, steep canyon that leads up to Mono Pass. Snow can linger late here and can be a significant problem.
The other side of the pass is a different world. All is barren, with decomposed granite covering the valley around Summit Lake and the gentle ridge on the west side. On the east side, steep, rocky slopes lead up to Mt. Starr. The far end of Summit Lake is only 0.5 miles and 150 feet lower than the pass. The lake is shallow and shrinks considerably after the snow has completely melted. Exposed camping is possible here, but good campsites are 1.3 miles farther at Trail Lakes.