Bald Mountain Trail, usually shortened to BMT, is the main hiking route up Baldy, the ski mountain that rises straight out of Ketchum. It starts at River Run Plaza, past the bike rental shop and to the right of the River Run chairlift, and climbs about 5.2 miles and 3,200 feet to a finish just west of the top of the Challenger lift near 8,990 feet.

Bald Mountain sits in the Smoky Mountains on the Sawtooth National Forest. Sun Valley Company runs the ski area under a Forest Service permit and manages the summer trail system, including BMT. The summit is 9,150 feet and the River Run base is about 5,750 feet, which gives Baldy roughly 3,400 feet of vertical.

The first stretch follows the Big Wood River before the trail turns uphill and starts switchbacking through a wooded drainage. Higher up it opens onto grassy slopes with views over Ketchum and the Wood River Valley, and a wooden overlook platform makes a good place to catch your breath. The average grade is about 12 percent, with a few short pitches much steeper. BMT crosses the Traverse and Saddle Up downhill bike trails, so look both ways at those crossings. Just past the junction with the hiker-only Roundhouse Connector you reach the stone memorial to Louis Stur and a water fountain.

The trail is open to hikers and to mountain bikers riding uphill only. It is directional, and downhill biking on BMT is not allowed. Riders who climb it usually come back down on French Connection or the Traverse, or they pick one of the other climbs, Cold Springs or Warm Springs, next time. Dogs need to be on a leash and e-bikes are not allowed. Sun Valley closes Bald Mountain to mountain bikes from November 1 through April 30.

A lot of hikers stop at the Roundhouse instead of going all the way to the top. Sun Valley puts it at about 4 miles one way via BMT, or around 8 miles round trip with about 2,000 feet of gain, and figures four and a half to five hours out and back at a moderate to hard effort. The Roundhouse sits at about 7,700 feet, and the Roundhouse Express Gondola covers the same climb in about eight minutes. Sun Valley suggests hiking up and riding the gondola down, which has run Wednesday through Sunday from 9 to 4 in summer. Visit Sun Valley notes that each gondola passenger needs a scenic ticket and that pets ride on a separate pass, so check ticket rules at River Run before counting on a ride down.

Baldy also has a lift-served downhill bike park with about 3,100 vertical feet of descending, which is listed separately. BMT is the way up for people who would rather earn it.

The 2026 season brought a lot of construction to the mountain. The Lookout and Christmas lifts are being replaced, Lookout Lodge is closed, the Saddle Up and Lupine trails are closed, and the City of Ketchum is building a connector from BMT over to Warm Springs. Since mid-September 2026 Sun Valley's summer trails report has listed BMT as closed with no estimated opening date, with Cold Springs as the only route to the top as an out and back. The new lifts are due for the 2026-27 winter. Check the summer trails report before heading up.