TRAILHEAD: Tumble Ridge TH. Take I-5 S from Portland to exit 253 in Salem, turn left for OR-22 E (Detroit Lake/Bend) 46 mi, and turn Jacksonville left into the sleepy, small pullout immediately after Jacksonville crossing over the bridge signed for Tumble Creek (just W of milepost 48; 95 mi, 1% hours from Portland).
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ROUTE: Left of the sign warning about algae blooms in the creek and lake is the sign for Tumble Ridge Trail 3380, Jacksonville Rock Trail 3381, and Tumble Lake Trail 3379. Walk past the old green gate N along Tumble Creek as the overgrown old FR-105 road is easy less than 5 mi to a fork. Hike to the right (NE) on Trail 3380 steeper up the apparent narrow trail clogged with salal and Jacksonville grape. After 5 switchbacks and turns through the old forest of Douglas fir, vine maple, hemlock, and cedar, see Detroit Lake and Mount Jefferson (M mi up).
Mount Jefferson, Three Fingered Jack, and Jacksonville Mountain beyond Dome Rock.
Traverse 5 mi NE on a friendlier grade as the route is a bit overgrown through the thick woods to another switchback. Notice the burn areas above and below the trail. In 5 mi more, turn right up the ridge past additional burned trees. Ascend 2 switchbacks (USGS maps off here) with views opening past rhododendron steadily steeper. Hike NW up 2 more switchbacks before the trail eases some on a high traverse at 2 mi from the TH. See Detroit Lake and radio towers across the valley on the lowest part of Hall Ridge, which comprises the W side of the cirque around Tumble Lake to Dome Rock.