USFS National Forest System Trails · Custer Gallatin National Forest · Montana · Updated June 2026
Hidden Lake Divide (USFS trail 66) is a 7.5 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 Hidden Lake Divide?
| Use | Status | Season on record |
|---|---|---|
| Mountain bike | Allowed | year-round |
| Class 1 e-bike (pedal-assist, 20 mph) | Allowed | Jul–Sep |
| Class 2 e-bike (throttle, 20 mph) | Allowed | Jul–Sep |
| Class 3 e-bike (pedal-assist, 28 mph) | Allowed | Jul–Sep |
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
Hidden Lake Divide (USFS trail 66) is a 7.5 mi trail in Custer Gallatin National Forest, Montana. 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. 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. The record additionally permits Class 1, Class 2, Class 3 e-bike use, Jul–Sep; 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. Because conditions, closures, and local orders change between data refreshes, confirm the current status with the managing ranger district before you ride.
Frequently asked questions
- Can you mountain bike on Hidden Lake Divide?
- Yes. Mountain bikes are designated as allowed on Hidden Lake Divide in Custer Gallatin National Forest, year-round, per USFS data.
- Are e-bikes allowed on Hidden Lake Divide?
- Class 1, Class 2, Class 3 e-bikes are designated on Hidden Lake Divide in the USFS data.
- How long is Hidden Lake Divide?
- Hidden Lake Divide measures about 7.5 mi in total, summed across its mapped National Forest System segments.
- What is the surface of Hidden Lake Divide?
- USFS data records the tread surface of Hidden Lake Divide as native material.
- How difficult is Hidden Lake Divide?
- 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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