USFS National Forest System Trails · Colville National Forest · Washington · Updated June 2026
Twin Sisters (USFS trail 109) is a 6.6 mi trail in Colville National Forest, Washington. Mountain-bike use here is accepted but discouraged in USFS data, with Class 1 e-bikes also designated.
Can I bike Twin Sisters?
| Use | Status | Season on record |
|---|---|---|
| Mountain bike | Accepted but discouraged | — |
| Class 1 e-bike (pedal-assist, 20 mph) | Allowed | Apr–Nov |
| Class 2 e-bike (throttle, 20 mph) | Allowed | Apr–Nov |
| Class 3 e-bike (pedal-assist, 28 mph) | Allowed | Apr–Nov |
Zooming out: across Colville National Forest, 8% of rideable trail miles are open to mountain bikes — a Bike Access Grade of F.
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About this trail
In Colville National Forest, Washington, Twin Sisters (USFS trail 109) covers 6.6 mi of National Forest System trail. This profile summarizes what the official US Forest Service trail record says about riding it: how long the trail is, what it's built on, how steep the route grades out, and which forms of bike use the agency has designated. Underfoot, the trail is recorded as native material. USFS slope data puts it in the Advanced band (grade band 12-20%), meaning a steep climb — keep in mind this measures steepness, not trail technicality. Note that mountain-bike use here is discouraged in USFS records — confirm with the ranger district before riding. The record additionally permits Class 1, Class 2, Class 3 e-bike use, Apr–Nov; 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 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 Colville National Forest.
Frequently asked questions
- Can you mountain bike on Twin Sisters?
- Mountain-bike use on Twin Sisters 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 Twin Sisters?
- Class 1, Class 2, Class 3 e-bikes are designated on Twin Sisters in the USFS data.
- How long is Twin Sisters?
- Twin Sisters measures about 6.6 mi in total, summed across its mapped National Forest System segments.
- What is the surface of Twin Sisters?
- USFS data records the tread surface of Twin Sisters as native material.
- How difficult is Twin Sisters?
- 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 Colville National Forest (USFS trail geometry isn't mapped).
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