How does that compare with a resupply over Kearsarge pass?
Kearsage Pass Trail Junction:
73 miles from Muir Trail Ranch
39 miles from Whitney Portal
+7.5 miles to Onion Valley Trailhead. (The packers bring it to Charlotte Lake). Still not centrally located for 1 resupply.
Baxter Pass Trail Junction:
66 miles from Muir Trail Ranch
46 miles from Whitney Portal
+11 miles over Baxter Pass to Oak Creek Trailhead. (The packers bring it to Woods Creek).
Baxter Pass or Woods Creek is the most central location for 1 resupply over the long southern section (112 miles from Muir Trail Ranch - Whitney Portal). That's why this is the most popular location for packer resupply on the JMT spreadsheet.
If you're going to leave resupply food in a bear box and hike to it, then Kearsage Pass is the best location due to the shorter hike to Onion Valley trailhead.
