The Tiger Mountain Trail (or TMT) traverses the 13,745-acre Tiger Mountain State Forest. The trail was conceived by members of the Seattle Mountaineers (and future members of the Issaquah Alps Trails Club) in 1972 and completed in 1979. It's construction spawned the building many other trails and the establishment of Tiger Mountain as a popular area for recreation.
This Washington Trails Association describes the details of the route (from south to north). It can be completed in either direction as a point-to-point. It meanders through beautiful forest and crosses several creeks as it passes by West, Middle and South Tiger Mountain summits.
Note added 2/4/2022: A small segment of the Tiger Mountain Trail has been rerouted due to logging as of about March 2021. The reroute is approximately 0.4 miles shorter, while the vertical gain has not changed, so the trail may now be slightly easier. We have updated our GPX track.
Ran the Tiger Mountain Trail from N to S, starting at 9:45 on a Sunday morning (11/13). As mentioned in the headnote, the trail has been rerouted due to a clear-cut at the top of the mountain. There may be an additional detour on the approach to the summit for restoration. It's unclear to me how recent that work is--it seemed like a relatively new sign.
I tried to run the full trail this summer but lost the trail in the clear-cut. Today there was snow at the top, which slowed the pace considerably, but made it easier to see the trail and navigate around the summit. Running this late in the season was helpful on the descent, as the vegetation was less dense than it seems to have been for others.
Finished in 2:45 and hope to try again in the future!