Finding old ruins is often a matter of catching a brief window in spring.
I found this set (above and below) early this past spring, after the daffodills bloomed, but before much else leafed out. The trail runs right through them, where the trail descends through a wide stretch of glades to turn in the valley bottom near a small spring, not far from the spur to Washington State Park's backpack camp.
Some of ruins are obvious, a set of rock and cement foundation pilings:
Other are less obvious, like this bit of pottery:
At first, I thought it was some sort of early camping cabin, but there's this bit of fence, perhaps from a latter time than the building ruins.
I have no real idea what went on here. There seems to be the remains of two structures, one not far from the spring (the one with the large pilings). And perhaps there are the remains of an earlier, less substantial structure farther back up the hill, on the slope. There seem to be uncemented foundation pilings there, and most most of the glass and pottery shards are nearby. But there's so little, if anything, left of the structure, that's its impossible to tell . . .