I inadvertently completed this route "on foot" as part of my Pacific Crest Trail thru-hike in 2019. At the time, I didn't even know this FKT existed, and I just wanted to climb some notable mountains off the main corridor of the PCT on my way south towards Mexico. As such, I did not time this well in terms of rest days, and I could've done this faster had I known I was competing for speed. I only note it here since it appears to be the OKT (only known time) for an entirely on-foot effort. I was hiking Southbound on the PCT, so my start and end points reflect that (starting at Islip Saddle in Angeles National Forest and finishing in Idyllwild near San Jacinto). The PCT doesn't actually summit these mountains, but I took the spur trails from the PCT via (1) North Backbone Trail to Mt. Baldy; (2) Fish Creek Trail to Mt. San Gorgonio; and (3) Deer Springs Trail to Mt. San Jacinto.
Having started at 7:19AM on 11/4/2019 and finished at 7:49PM on 11/12/2019 makes this a total of 8 days, 12 hours, and 30 minutes covering 246.43 miles and 44,714' of gain. Not nearly as fast as the sub-24h efforts of those using vehicles for transport, but it's cool to do this entirely "on foot".
11/4/2019 (7:19AM) -- Islip Saddle to Baldy via North Backbone Trail to Wrightwood:
https://www.strava.com/activities/2843005132
11/5/2019 -- Rest day in Wrightwood
11/6/2019 -- Wrightwood to Little Bear Spring Trail Camp via a continuous 33h effort:
https://www.strava.com/activities/2851109869
11/8/2019 -- Little Bear Spring to Big Bear:
https://www.strava.com/activities/2851110911
11/9/2019 -- Big Bear to Coon Creek:
https://www.strava.com/activities/2858849666
11/10/2019 -- Coon Creek to Fish Creek via San Gorgonio:
https://www.strava.com/activities/2858850793
11/11/2019 -- Fish Creek to base of San Jacinto:
https://www.strava.com/activities/2859031953
11/12/2019 -- Climbing San Jacinto to Idyllwild:
https://www.strava.com/activities/2861484452
I submit this as a "supported" FKT for a variety of reasons: I hiked with people; I stayed at a hotel in Wrightwood and in Big Bear and got groceries; I got rides into and out of Big Bear (but I picked up where I left off on the trail). I did things as a PCT thru-hiker does. But I walked every step of the route under my own power.
It was a wild time out there. I broke a tooth eating a chocolate bar; I hallucinated a bear on the trail in front of me; I randomly encountered friends that I hadn't seen in months; I ate a meal enough for 6 people at McDonalds; I soaked in Deep Creek hot springs; and on one section, I completed a 33h continuous hike through the deserts and mountains of Southern California. Great memories (except for the broken tooth)!