South O'Brien Loop
USFS trail 123
The route in 3D
Fly this trail over real terrain
USGS and partner elevation data build the terrain, and the US Forest Service centerline draws the route.
7.8 mi · Typical grade 10 to 12%
About 800 ft between the route's high and low points. An estimate from US government elevation data, computed 2026-07-11; not measured in the field.
Trail facts
- Length
- 7.8 mi mapped
- Grade
- Typical grade 10 to 12%
- Surface
- native material
- USFS-managed uses
- Horseback (pack and saddle)
- Motorized status
- Non-motorized (USFS designation)
- Designation
- National trail designation
- National forest
- Lolo National Forest
Length is the trail as the Forest Service maps it, not a trip distance. Hike out and back and you will cover it twice; check the shape of the route before you count on the figure.
This record is a snapshot of U.S. Forest Service data retrieved on 2026-07-09. It does not reflect current closures, conditions, or seasonal orders. Check with the local ranger district before you go.
Elevation
About 880 ft of climbing around the loop.
- High point
- About 4,350 ft
- Low point
- About 3,550 ft
Estimates, derived from US government elevation data sampled along the USFS-mapped route, computed 2026-07-11. We have not measured these figures in the field.
Plan a day on this trail
A day here means a typical grade of 10 to 12%. Tell the Trip Builder where you are headed and it assembles a day-specific kit with weather, daylight, and terrain in mind.
Build your kitData: U.S. Forest Service, retrieved 2026-07-09.