If I recall past discussions, I think the 13,777 was considered a mapping or printing error.

...In fact, I went searching, and the late Wayne Pyle, (a true mapping enthusiast -- he mapped the 99 switchbacks )
wrote this in this topic: My epic photo of the 97 switchbacks (at night!)

Originally Posted By: Wayne, 11/12/2011
Kurt,

Wow! Most excellent work! That is a fabulous photo, and I think an amazing photographic accomplishment.

In your write-up, you cite the top of the switchbacks at Trail Crest at 13,777 feet. Unfortunately, someone many years ago misread an old (early 1900s or early 1940s) topographical map that showed that figure, but the elevation-figure was meant for the Discovery Pinnacle--not Trail Crest. The figure was printed on the map at Trail Crest, but meant for Discovery. Several years ago the Forest Service discovered the mistake and changed Trail Crest's elevation to 13,600 feet and replaced the trail sign at Trail Crest with the corrected elevation. (USGS has since lowered the height of Discovery to 13,750 feet.)

Thanks for posting!