Sacagawea is the next peak south of Borah Peak, the Idaho state highpoint. Sacagawea sits on the main Lost River crest, joined to Borah's Chickenout Ridge (standard route) by a narrow, rocky ridge with a saddle that drops about 500'.
The standard route offers a really fun, although tiring, classic Lost River Range ridge scramble-- after you have gained the ridge. The first part to the ridge is mostly your basic uphill grunt.
Standard Route Stats
Most of this information, including the Getting There and other sections, applies to the standard route.
Climb: ~4 miles, 4780' gain. Plan on 5-8 hours
Descent: Same route with ~500' climb on return. Plan on 4-6 hours
For more route info, see that section below.
In addition to the standard route discussed here, there may be a Class II route possible up Cedar Creek and then up Sacagawea's south side. However, this route would be an extremely long, tedious talus slog with little to recommend it except gaining the summit.
There have been attempts at other routes, including the huge east face. These have been much more technical, or unsuccessful. Two successful routes include Gold Digger and the North Face Direct. Either of these is accessed from the east side of the range. Gold Digger ascends a subsidiary point on Sacagawea's ridge via an ice smear that is only rarely in condition. The North Face Direct is a technical rock climb and tremendous adventure, established by SPer SkunkApe.
Driving from Mackay
Go north on Hwy 93 for about 21 miles and turn right (east) onto the Borah Peak Access Road (Birch Springs Road). This turnoff is between mileposts 129 and 130. In 3.0 miles, the road dead-ends at the trailhead.
Driving from Challis
Go south on Hwy 93 for about 33 miles and turn left (east) onto the Borah Peak Access Road. This turnoff is not well marked from the north, but it is between mileposts 129 and 130. The road dead-ends in 3.0 miles at the trailhead.
The Borah Peak Access Road road is improved dirt. In good weather, it is suitable for passenger cars. When wet, it can be a slick, muddy trap.
During the "off-season" the road may be dry but can drift with snow, so be prepared to walk from the pavement.
The trail leaves from the uphill side (east) of the parking lot. There is a small kiosk with advice from your caring government and an obvious gate through the fence.
No red tape.
No passes, register, or other stuff. You're on your own here, so use appropriate caution.
There is very primitive camping at the Borah trailhead area. Although there is a nice concrete toilet, the only camping amenities are a few picnic tables and an unlimited supply of free mosquitoes.
Some prefer to camp at any of the other campgrounds shown on Forest Service or BLM maps of the surrounding area, several of which are less than 20 miles away. These generally will have more facilities, potable water, etc.
If you would prefer something more comfortable, there are several nice, inexpensive motels in Mackay.
Start by following the standard Borah route
Start by climbing the standard route for Borah Peak. A good trail (loose and steep, but obvious) gets you up the first 3500' of gain to the bottom of Chickenout Ridge. Cross this airy ridge section until you reach the obvious saddle.
Leave the Borah route after Chickenout
From the saddle after Chickenout, the standard Borah route does a flat traverse to climber's left. DO NOT take that trail. Instead, continue straight up the spine of the ridge toward a bump or false summit. At or near the top of this bump, you will see the NW ridge of Sacagawea. Traverse (scramble) to the ridge when you find it convenient. The least technical way is to go to the top of the bump.
Traverse the ridge to the Sacagawea saddle
Follow the ridge toward the peak, staying on or near the ridge top, until you reach the saddle in the ridge.
Cross the gullies
From the saddle, drop down slightly to climber's right and traverse several gullies. Depending on your route and choices, you should cross either three or four. Then regain the ridge top.
Climb the Class IV headwall
If you choose wisely, there is really only one section of Class IV. The final headwall is maybe 40 or 50 feet high. From there, it is a short ridge scramble to the summit.
Note that it may be possible to bypass this section by doing a scree traverse beneath it. Others have reported doing so, although the route descriptions are vague enough to not be useful here.
A word of caution
If I forgot to mention it, the rock on this route tends to be loose. Helmet recommended. It is also sharp, so leather gloves are not a bad idea. Descending the Class IV section is a little tricky due to the loose nature. Some may prefer to rap.
For additional information on this climb and other peaks in the area, please see Tom Lopez's excellent book, Idaho: A Climbing Guide.