Uinta Highline Trail (not doing it this year or next year, but maybe after that, in a late August and early September week and a half or so.) If you look online, you may find that there's some confusion as exactly where the terminuses (termini?) for the trail actually lie. The Highline Trailhead on Mirror Lake Highway is universally agreed to be one end of it, but there's a lot of folks who claim Chepeta Lake out east is the eastern terminus. Maps will easily show that the trail continues to Hacking Lake No. 1, also sometimes called the Leidy Peak trailhead. But if you look at the next map, which continues east past this destination, you will see that the trail actually goes all the way to US-191 (see image.)
However, of course there's always more to the story. If the point of the Highline Trail is to hike the spine of the Uinta Mountains, if you map it on Google Earth with the Uintas, something quite odd becomes immediately apparent. I found where someone had done exactly that, I took that image and made a few modifications to it myself. Have a look:
Just looking at the topography, it's obvious that the section of the trail between US-191 and Leidy Peak differs dramatically from the section to the west of that. How is that a hike through the high spine of the Uintas? According to the map, it isn't really. It's a hike through the lower eastern "Bollies" section of the range, which differs in nature from the core of the range.
Given that, I'm comfortable saying that the trail itself may go all the way east to US-191, but I wouldn't say that its part of the same experience. The section that I would ignore and not hike is the darker orange section. I'd start at Leidy Peak.
You'll also notice the section in yellow on the far west. I drew this in myself by following the actual highline of the range to it's conclusion. The trail ends at the little red arrow where the medium orange stops. The yellow section is not part of the Highline Trail, but based on the topography, it belongs on the trail much more than the US-191 to Leidy Peak section does.
Sadly, it might be a bit problematic. You'd have to stitch together various forest service trails and bushwhacking, and even then it might not be possible, since not all of that section is public land anyway. I'm curious to pore over my map of the area in the next little bit to see if a route more or less corresponding to the yellow section of the trail could even be put together or not. If one can be constructed, I'd love to plan a hike of the medium orange and yellow sections of the trail... but I'll save the dark orange for some other day when I don't have other more interesting hikes to aspire to instead.
Not that anyone reads this blog, but I'm very curious if anyone has ever attempted to stitch together a western spur to the Highline Trail that goes from SR-150 to Kamas through the actual spine of the mountain range or not. I bet you could easily hike at least half of it before you started running into trouble.