Burley Mountain is an obscure 5403' summit located seven miles east of Index, and seven miles north of Skykomish. Surrounded by several 6000'+ peaks, Burley Mountain does not receive much attention from local climbers. Truthfully, I even have a hard time recommending it myself. For half the effort, one can ascend nearby Townsend Mountain (0.8 miles south), which offers generous unobstructed views.
Having said that, for those who have 'knocked off' Baring, Gunn, Merchant, Townsend, and Spire, Burley Mountain offers the chance to penetrate the heart of the Wild Sky Wilderness, and offers a healthy 903' of prominence for peakbaggers. For those with a lake fetish, three alpine lakes within 1/2 mile of the summit (Sunset, Simms, Fourth of July) will provide extra incentive.
As Burley Mountain lies smack dab in the middle of a large area bound by the North Fork Skykomish, South Fork Skykomish, and Beckler Rivers, there are understandably several possible ways to access it. I will only describe what I believe to be the easiest and shortest approach, with only brief consideration given to the others.
Navigate yourself to the beginning of the Beckler River Road (FR65), located 0.8 miles east of Skykomish on US2. Follow FR65 for only 0.6 miles, then turn left on FR6510. After a short distance, stay right on FR6510 (ignoring FR6512) at the first fork. Ignore a right hand turn at 1.0 miles and stay on the mainline, which now has the designation FR6514. At 4.8 miles (FR6514/FR6516 intersection), the road will get fairly rough. If not equipped with four wheel drive, plan to park here. If four wheel drive equipped, continue up FR6514 (right fork). Stay on FR6514 for an additional 1.4 miles, to a marked trailhead for the unofficial Eagle Lake trail.
As an alternative for getting to Eagle Lake, one could hike in via Barclay Lake (described on Townsend Mountain page). This will add distance and elevation, but the trailhead is accessible to all vehicles.
Follow the Eagle Lake trail for approximately 1.8 miles to the outlet (east side) of Eagle Lake in Paradise Meadows. Now head northeast toward a 5460' saddle located 0.3 miles west of Townsend Mountain.
It will be steep, but not harder than class 2 if you approximate the route shown on the map. Unfortunately, the vegetation on the steep slopes below the saddle will be frustratingly slick if covered in moisture or dew.
From the saddle, travel about 100 yards east toward Townsend Mountain (easier than descending directly from the saddle), then drop northwest into an obvious basin at 5100'.
From the basin, turn northeast, and descend toward a 4500' saddle immediately west of Forth of July Lake.
You will encounter some steep talus and scree scrambling on the way to the Burley/Townsend saddle, but the route should be fairly obvious. If at any time you find anything harder than class 3, you are doing something wrong (mostly class 2). From the Burley/Townsend saddle, proceed north up mixed timber and talus toward Burley Mountain's summit. For the final 100', plan a clockwise traverse to the summit block on Burley's gentle north slopes.
Alternate approach: This was the way I originally intended to scramble Burley Mountain, but I was put off by the poor condition of the access road. From US2, drive about 9.4 miles up FR65 (Beckler River Road) to an obvious left hand turn (elev. 1904'). Follow this road 0.7 miles to an intersection at 2169'. Turn right, and drive up this road as far as you dare. Maps show this road stretching toward the Northwest Ridge of Burley Mountain at 4300'. From this point, the scramble to the summit area should be fairly straightforward.
Another possible approach to Burley Mountain would be via Trout Creek and Sunset Lake, but this route is completely untested by yours truly.
From a distance, Burley Mountain does not appear to be that great of a viewpoint. Closer inspection, however, reveals several rocky promontories that allow one to peak above the trees. By visiting two or three of these closely spaced locations, views in all directions can be obtained.
A Northwest Forest Pass will only be required for those choosing the 'Barclay Lake' approach option.
June through October would probably work best for the Eagle Lake approaches.
Several possibilities: Beckler River Campground on FR65, Paradise Meadow/Eagle Lake, Sunset Lake, Lake Simms, Fourth of July Lake. Additionally, just northeast of Burley Mountain's summit is a large, flat meadow that would make an excellent camping location.