Union Falls, Waterfall in Yellowstone National Park, Wyoming, US

Union Falls is a waterfall in Yellowstone National Park where water drops 250 feet (76 m) down the mountainside in wide, curtain-like sheets. The cascade originates from Mountain Ash Creek and creates a powerful display as it falls against the exposed rock face.

A survey team led by Arnold Hague documented and named this waterfall between 1884 and 1886 during their geological exploration of Yellowstone. The team noted how the water converges at the meeting point of two creeks.

The name comes from the meeting of waters: a tributary of Mountain Ash Creek joins at the very brink of the falls, so the Arnold Hague survey members called it Union Falls. Geologist J.P. Iddings recorded this explanation. Visitors reach the brink via the Mountain Ash Creek trail and the Grassy Lake Road.

The hike to this waterfall starts at Grassy Lake Trailhead and covers about 16 miles total distance through thick forest and backcountry. Expect river crossings along the way and bring adequate supplies and proper hiking gear for the remote terrain.

The name comes from a tributary of Mountain Ash Creek that joins the creek right at the brink of the drop, so the two streams unite as they fall. Geologist J.P. Iddings, who worked on the Arnold Hague surveys, recorded this explanation for the name.