This trail is the shortest approach for those wishing to climb Grayback Mountain, the highest peak in Josephine County, Oregon. It also provides access to the northern end of the Boundary Trail #1207
This trail has an upper and a lower trailhead, both are on Forest Road 1005. The upper trailhead has limited parking and the stretch of FR 1005 leading to it can be rough going for passenger cars. If in doubt, park at the roomier lower trailhead and follow the #900 trail up along O'Brien Creek. It's a pleasant run along the creek and better than wreaking your car.
From the lower trailhead, the trail climbs along the north side of O'Brien Creek for two miles up a moderately steep slope with a few steeper sections. The trail will cross the creek; here there is a side trail that will take you to the Grayback Snow Shelter - a cabin that was used before snow surveys were automated and is now used by runners and backpackers - and past the cabin to the site (now marked with an old stove) - of the Krause Cabin.
To continue on O'Brien Creek Trail #900, cross the creek and ascend a few long switchbacks. The trail ends at the Boundary Trail #1207
and is marked with a classic old wooden sign.
Here you have the option to go north or south on the Boundary Trail #1207
for a cross-country scramble to the summit of Grayback Mountain from either Windy Gap (almost no brush) or up the ridge just south of Cold Spring (lots of brush if you lose the use trail).