USFS National Forest System Trails · Salmon-Challis National Forest · Idaho · Updated June 2026
Darling-Castle Creek (USFS trail 4138) is a 20.9 mi trail in Salmon-Challis National Forest, Idaho. Mountain-bike use here is accepted but discouraged in USFS data, with Class 1 e-bikes also designated.
Can I bike Darling-Castle Creek?
| Use | Status | Season on record |
|---|---|---|
| Mountain bike | Accepted but discouraged | — |
| Class 1 e-bike (pedal-assist, 20 mph) | Allowed | year-round |
| Class 2 e-bike (throttle, 20 mph) | Allowed | year-round |
| Class 3 e-bike (pedal-assist, 28 mph) | Allowed | year-round |
Zooming out: across Salmon-Challis National Forest, 26% of rideable trail miles are open to mountain bikes — a Bike Access Grade of C.
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About this trail
In Salmon-Challis National Forest, Idaho, Darling-Castle Creek (USFS trail 4138) covers 20.9 mi of National Forest System trail. The figures here are pulled from the official US Forest Service trail data for Salmon-Challis National Forest, covering the trail's mileage, tread, grade band, and the bike and e-bike uses the agency lists as designated. Underfoot, the trail is recorded 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. For traditional mountain bikes, use is discouraged according to USFS data. The record additionally permits Class 1, Class 2, Class 3 e-bike use; recall that Class 1 is pedal-assist, while Class 2 adds a throttle and Class 3 a higher cutoff speed. The route is mapped as USFS Trail Class 2 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 Salmon-Challis National Forest.
Frequently asked questions
- Can you mountain bike on Darling-Castle Creek?
- Mountain-bike use on Darling-Castle Creek is discouraged in USFS records, though Class 1 e-bike use is designated. Confirm current rules with the managing ranger district.
- Are e-bikes allowed on Darling-Castle Creek?
- Class 1, Class 2, Class 3 e-bikes are designated on Darling-Castle Creek in the USFS data.
- How long is Darling-Castle Creek?
- Darling-Castle Creek measures about 20.9 mi in total, summed across its mapped National Forest System segments.
- What is the surface of Darling-Castle Creek?
- USFS data records the tread surface of Darling-Castle Creek as native material.
- How difficult is Darling-Castle Creek?
- 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 Salmon-Challis National Forest (USFS trail geometry isn't mapped).
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