Obelisk Lake is a favorite spot in the park for a small handfull of people, most of whom work either at the Mereced lake High Camp or the nearby ranger station. It is not a long hike by any means, but since most of it is cross-country, allow a lot more time than you would on a trail. Also, it is essential to try to tread lightly. Follow established trails where possible, including the traces of the old cavalry trail where visible. When there is no obvious trail, try to walk on rock wherever you can. If you absolutely must walk one fragile ground, remember not to follow one another, but to spread out your impact. Above all, stick to dry ground and do not walk through bog or marsh under any circumstances. That type of ground is fragile and your footprints may be visible for years. Go the extra distance and go around.
You will probably want to approach this from the Merced Lake High Sierra Camp, which can be reached by any number of trails. Some possibilities are
- From Yosemite Valley take the John Muir Trail or the Mist Trail to Little Yosemite Valley (LYV) and then follow the Merced River to the high camp.
- From Glacier Point take the Panorama Trail to LYV and then as for the Mist Trail.
- From Vogelsang High Camp, picking up the route described below at the Merced Lake Ranger station.
In any case, the "trailhead" for this route is a going to be at least nine miles from where you park your car so it's a quite difficult day hike. We have done it in a day from Glacier Point, but this is almost 40 miles of walking, with roughly 8-10 miles of that cross-country, so it's quite a hump and doesn't leave you much time to really enjoy Obelisk Lake and explore the highlands around it.
From the Merced Lake High Sierra Camp, follow the trail toward Vogelsang for about 1.5 miles past the Merced Lake Ranger Station (about .75 miles) to a point where the trail comes back close to the Merced River. At this point, look for a crossing tree over the river if possible, otherwise prepare to ford the river. Be aware that in high water during spring runoff, this could present a serious obstacle, not to mention danger of drowning or hypothermia if you fall into the icy water. Don't take this too lightly.
Once across the river, you want to attain the slopes above the Gray Peak Fork of the Merced. There are some beautiful waterfalls and rushing water here that are worth a look, but in general you will keep your distance from the Gray Peak Fork because it is quite a bit lower than the surrounding slopes. Make your way through the gentle wooded banks near the Merced River and keep your eyes out for cairns, trails or the traces of stonework from the switchbacks on the old cavalry trail. There are a couple of drainages between the Gray Peak Fork and the best trail through the lower sections of manzanita. Once you find the trail, in less than a mile of steep thrashing, it will bring you out onto open slabs above the Gray Peak Fork that are your best route across this section. There are great views here and some fabulous stunded Western Junipers that look like they have survived some hard times in their long lives (some of the longest-lived trees in the Sierra after the Sequoias). At somewhere roughly around 8400' you'll go back into the forest and eventually contour along rising slightly to roughly 8600' until you get to the creek that drains down slabs from Obelisk Lake with stunning views of a sharp ridge and spur on Mount Clark. One of my shots from this point will be gracing the cover of the Trails Illustrated map for the region. At this point, you've only gone a mile or so from the Merced River, but plan on investing 1-2 hours to cover that distance if you haven't been there before.
From here, follow the creek up the north side as it cascades over slabs, making long traverses on deer trails when you near the top of the slabs. Once off the steep part, you'll find yourself in a fairly lush, well-watered shallow valley with beds of green and nice displays of Leichtlin's Mariposa Lillies in the right season. Once again, be kind to the land here and stay on the dry, rocky areas as much as possible so that others after you can experience these lush green meadows and marshes without footprints. You'll want to cross the creek to the south and hike comfortably on gentle slopes, crossing it again (to the west side now, as it has turned 90 degrees) and obtain the rounded ridge that begins at around 9300' and ultimately takes you to Obelisk Lake at 9853 feet. The total distance will be roughly 5 miles from the Merced Lake High Camp, depending on how much switchback and so forth.
To return, just retrace your steps.