wherever and chick-on have covered the Indian Canyon "trail" scramble already:
http://yosemitenews.info/forum/read.php?3,29137,29137#msg-29137
http://yosemitenews.info/forum/read.php?3,25265,26069#msg-26069
http://yosemitenews.info/forum/read.php?3,36903,36905#msg-36905
Indian Canyon is the canyon to the right (east) of Yosemite Falls when looking at the falls head-on; the mouth of it is near Church Bowl. James Hutchings paid to have a (toll) horse trail built up Indian Canyon in 1874, but it fell into disrepair only a few years later due to the difficulty of maintaining it. It didn't help that Conway had built the nearby more scenic trail to the top of Yosemite Falls around the same time.
The "junction" with this trail and the portion of the valley loop trail between Lower Yosemite Falls and Church Bowl is roughly 100 yards east of an open talus field that is near the highest part of the trail in this section. When I was there it was marked by a few ducks, and in fact the lower several switchbacks were similarly ducked--probably because the trail is used as a climbers' access route.
For some reason I was expecting a minimally-constructed trail, but in fact this trail had been built to about the same standard as the Yosemite Falls trail. The trail was about 3' wide and had substantial rock work. The trail is surprisingly well preserved below 5000' and above 6000'; between these elevations, either I was far off-route, or it was obliterated by rockfall.
In several places mature trees and bushes are growing in the middle of what should be (based on the rock work) the trail. This was annoying since it was always easier to follow the trail than to scramble around, and in many places the trail's condition was not consistent with having a mature oak tree or manzanita bush growing in it.
The on-"trail" portions were mostly fine, but the middle section was rough-going. The steepness was bad enough, but the slope in these sections is very unstable--footing was often a challenge. In these sections my progress was one step at a time, and more than a few times I "aid-climbed" by pulling on branches and bushes. I kicked a few rocks down that tumbled for what seemed to be hundreds of feet. Towards the top, one steep section was covered with 6" of slippery Jeffrery pine needles. In these sections it's not at all surprising that the trail was hard to maintain--or that there are no signs of it any more. Or, perhaps it's more surprising that so much of this trail still remains.
In short, for someone who likes finding and following old trails, or just likes a good scramble, Indian Canyon provides a way to make a shorter north-valley loop--although I'd still recommend the Snow Creek/North Dome/Yosemite Falls trails instead. The views are decent--but the Yos. Falls, Four Mile, and Snow Creek trails are all better.
That said, going down Indian Canyon may be preferable to the sand-on-bowling-balls slip-sliding experience that the Yosemite Falls trail has become...
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