This long-abandoned trail is somewhat out of our area. It is in the Ross Lake Natl Recreation Area rather than North Cascades NP so my beloved dog Hysson is allowed. It's accessed from 4th of July Pass which can be reached either from the Panther Creek trailhead along WA 20 below Rainy Pass or from the Thunder Creek trailhead from the Colonial Cr. Campground lower down on WA 20. There was once a trail up Ruby Mountain. I was up there with a group about 15 years ago, and the trail was long abandoned, but still easily findable both from the grade that was still there and from the scars of the USFS double blazes (long blaze with short on top, like an inverted !).
Since the USFS blazed both sides of the tree facing the trail, if there's a question about whether the trail curves or switches back, look for the scar of the blaze on the other side of the tree (I had lots of experience finding abandoned trails in northern CO as a teenager). Lots of blowdowns (mostly smaller trees) but far easier than bushwhacking. Our group tried bushwhacking up but never made it because a big (for this part of the country) thunderstorm came up.
We found the trail on the way back down, which made our descent easier and quicker. Take the trail E from 4th of July Pass Camp towards Panther Cr. It goes into a rather spooky looking half-dead forest. Cross a wooden bridge over a boggy area. Just east of the bridge was a sign saying "Trail Closed." That was the trailhead. At that time a few guys with saws could have re-opened the trail quite easily--it was in good condition except for the blowdowns, most of which could easily be stepped over. Per nwhikers.net, a few people each year still go up it--here's a trip report with spectacular pics:
http://www.nwhikers.net/forums/viewtopic.php?t=15029
This guy bushwhacked up Ruby, though, and didn't hit the trail until he got near the top. The NPS once wanted a gondola to the top of Ruby, but fortunately that idea was shot down. 4th of July Pass is a great destination in itself. When we were there (4th of July weekend, of course), from our camp we had spectacular views not only of Colonial Peak and Colonial Glacier but of enormous waterfalls descending from the glacier--at least on the rare occasions that wet weekend when there wasn't water falling out of the sky! | 
