Rock Island Lake Trail

Rock Island Lake Trail is an out-and-back from the signed Clarks Fork Trailhead to a high mountain lake. The mapped corridor is 3.39 miles each way, or about 6.8 miles round trip; allow around three to four hours. It is not a steep summit hike, but the distance, rolling footing and 8,000-foot elevation make this a real half-day walk. Go for the lake and the changing route, not for a quick roadside stroll.

The walk starts across a bridge over the Clarks Fork of the Yellowstone, above rapids; downstream the river settles into a clear pool. The single-track climbs through timber. At the Kersey Lake junction, stay on the uphill route instead of dropping toward the lake, then continue straight at the Vernon Lake branch. A high point opens a view across Kersey Lake, though the trail does not circle its shore.

Past marshes and small ponds, a sturdy bridge crosses a broad wet area before the grade rises a little. Just beyond the wilderness boundary, look for the right-hand branch to Rock Island Lake. It is easy to miss, and maps disagree whether the spur is numbered 565 or 566; the route to the lake is the important cue. Continuing a short way beyond that junction leads toward Crazy Lakes instead. The final spur is about two-thirds of a mile to the lake; return the same way.

Rock Island Lake sits around 8,180 feet. It is a quiet-feeling high-country finish after a mostly wooded approach, with the lake and surrounding ridges opening up at the end. The lake supports brook trout and stocked Yellowstone cutthroat. Moose are sometimes reported around the nearby wet ground, but sightings are never a sure thing.

Start at the signed Clarks Fork Trailhead off US 212; beginning at the separate Kersey Lake access changes the route and mileage. Beartooth Highway access is usually seasonal, roughly late May into early October, with dates varying by year. No toilets or potable water at this trailhead were confirmed, so bring what you need and treat any backcountry water. Dogs are allowed; keep them under control and pack out waste. This is bear country, so carry bear spray.