USFS National Forest System Trails · Custer Gallatin National Forest · Montana · Updated June 2026
Skyline (USFS trail 151) is a 20.8 mi trail in Custer Gallatin National Forest, Montana. Mountain bikes are designated as allowed year-round, with Class 1 e-bikes also designated.
Can I bike Skyline?
| Use | Status | Season on record |
|---|---|---|
| Mountain bike | Allowed | year-round |
| Class 1 e-bike (pedal-assist, 20 mph) | Allowed | Jul–Dec |
| Class 2 e-bike (throttle, 20 mph) | Allowed | Jul–Dec |
| Class 3 e-bike (pedal-assist, 28 mph) | Allowed | Jul–Dec |
Zooming out: across Custer Gallatin National Forest, 98% of rideable trail miles are open to mountain bikes — a Bike Access Grade of A.
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About this trail
In Custer Gallatin National Forest, Montana, Skyline (USFS trail 151) covers 20.8 mi of National Forest System trail. The figures here are pulled from the official US Forest Service trail data for Custer Gallatin National Forest, covering the trail's mileage, tread, grade band, and the bike and e-bike uses the agency lists as designated. The tread is mapped as native material. Based on slope, this is a Advanced trail (grade band +12-20%); that reflects steep gradient and is not the same as a technical MTB difficulty rating. Bike use is designated as allowed year-round. On the electric side, Class 1, Class 2, Class 3 e-bikes are also designated (Jul–Dec) — Class 1 being pedal-assist only, Classes 2 and 3 adding a throttle and higher assisted speed. The route is mapped as USFS Trail Class 3 on the agency's 1-to-5 development scale, where 1 is the most primitive, minimally maintained tread and 5 is the most developed. Treat this as a planning reference rather than a live conditions report, and verify any time-sensitive closure or order with the ranger district that manages Custer Gallatin National Forest.
Frequently asked questions
- Can you mountain bike on Skyline?
- Yes. Mountain bikes are designated as allowed on Skyline in Custer Gallatin National Forest, year-round, per USFS data.
- Are e-bikes allowed on Skyline?
- Class 1, Class 2, Class 3 e-bikes are designated on Skyline in the USFS data.
- How long is Skyline?
- Skyline measures about 20.8 mi in total, summed across its mapped National Forest System segments.
- What is the surface of Skyline?
- USFS data records the tread surface of Skyline as native material.
- How difficult is Skyline?
- Its grade-based difficulty is Advanced (grade band +12-20%), derived from USFS slope data. This reflects steepness, not technical mountain-bike difficulty.
How we read this data
Grade-based difficulty above is the USFS grade (route steepness), not a technical mountain-bike rating — a gentle-grade trail can still be rocky or technical, and vice versa. Bike and e-bike status come verbatim from the USFS managed-use fields for this trail; we never infer access we can't cite. See our methodology for how the dataset is built and what each field means.
Where it is
Approximate location of Custer Gallatin National Forest (USFS trail geometry isn't mapped).
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