USFS National Forest System Trails · Caribou-Targhee National Forest · Idaho · Updated June 2026
Spring Run 120 (USFS trail 4120) is a 2.1 mi trail in Caribou-Targhee National Forest, Idaho. Mountain bikes are designated as allowed year-round, with no Class 1 e-bike designation on record.
Can I bike Spring Run 120?
| Use | Status | Season on record |
|---|---|---|
| Mountain bike | Allowed | year-round |
| Class 1 e-bike (pedal-assist, 20 mph) | — | |
| Class 2 e-bike (throttle, 20 mph) | — | |
| Class 3 e-bike (pedal-assist, 28 mph) | — |
Zooming out: across Caribou-Targhee 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
Spring Run 120 (USFS trail 4120) is a 2.1 mi trail in Caribou-Targhee National Forest, Idaho. The figures here are pulled from the official US Forest Service trail data for Caribou-Targhee National Forest, covering the trail's mileage, tread, grade band, and the bike and e-bike uses the agency lists as designated. USFS records list its surface as native material. Its grade-based difficulty is Advanced (grade band +12-20%) — a steep steepness profile derived from USFS slope data, not a technical mountain-bike rating. Bike use is designated as allowed year-round. No e-bike class (1, 2 or 3) is designated on this trail in the USFS data, so treat it as a non-motorized route unless a posted order says otherwise. 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 Caribou-Targhee National Forest.
Frequently asked questions
- Can you mountain bike on Spring Run 120?
- Yes. Mountain bikes are designated as allowed on Spring Run 120 in Caribou-Targhee National Forest, year-round, per USFS data.
- Are e-bikes allowed on Spring Run 120?
- No e-bike class (1, 2 or 3) is designated on Spring Run 120 in the USFS data.
- How long is Spring Run 120?
- Spring Run 120 measures about 2.1 mi in total, summed across its mapped National Forest System segments.
- What is the surface of Spring Run 120?
- USFS data records the tread surface of Spring Run 120 as native material.
- How difficult is Spring Run 120?
- 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 Caribou-Targhee National Forest (USFS trail geometry isn't mapped).
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