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At about 260 feet, Union Falls is the second-tallest waterfall in Yellowstone, fanning out dramatically in the remote Bechler (Cascade Corner) region. Reaching it requires a long backcountry day hike or backpack of roughly 16 miles round trip.

Height
260 ft
Type
Fan
Access
Backcountry
Trail
15.6 mi out-and-back
Elevation gain
Not documented
Best season
Mid-July to September
Land manager
National Park Service (Yellowstone National Park)
Watercourse
Mountain Ash Creek

Before you go

Waterfalls are hazardous by nature — wet rock, cold water, and unstable edges — and flow varies enormously with season and recent rain. Trail figures here describe the route as documented, not conditions today. Check National Park Service (Yellowstone National Park) for closures and current conditions, and confirm land status before setting out.

Graded lakes within 25 miles

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Frequently Asked Questions

Union Falls drops about 260 feet. That makes it the 57th-tallest documented waterfall in this inventory, taller than roughly 92% of the falls listed here. Height comes from published land-manager and survey records, not from our own measurement.

The Mountain Ash Creek / Union Falls Trail (from Grassy Lake Reservoir) reaches it about 15.6 miles (out-and-back), rated strenuous. The nearest town is Ashton, Idaho. That describes the route as documented, not conditions on the day — check with National Park Service (Yellowstone National Park) for closures and current conditions.

Mid-July to September. Waterfall flow swings enormously with snowmelt and recent rain, so a fall that roars in spring can be a trickle by late summer.

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