Big Falls is an 87-foot waterfall on the Missouri River in Cascade County, Montana, the lowermost and largest of the five Great Falls of the Missouri that Lewis and Clark had to portage around in 1805. Ryan Dam now sits directly above it, and the falls are viewed from Ryan Island Park, a day-use area reached by a suspension bridge.
The falls
The river breaks over a single, segmented ledge about 600 feet wide; at peak flow it can spread to 900 feet. The long-published figure is 89 feet. Ryan Dam, built in 1915, diverts most of the river to its hydroelectric plant for much of the year, often leaving the falls a trickle. Counting the dam, the combined drop reaches 148 feet.
Getting there
Ryan Island Park is at 160 Ryan Dam Road. From Great Falls, head north on US 87 for 3 miles, turn right on Morony Dam Road for 6.5 miles, then bear right onto Ryan Dam Road. NorthWestern Energy runs the site, which is open from Mother's Day through Labor Day, daylight to dark, seven days a week; outside that season the island is closed. Picnicking is free and needs no reservation.
When to go
Spring is the best time, when the falls are loudest. In summer the dam takes most of the water.
On site
A suspension bridge crosses to the island, where a fenced overlook sits on the cliff top above the falls. The island has picnic shelters, interpretive displays, restrooms and access to the River's Edge Trail, and a clubhouse that can be reserved free of charge. The picnic area and clubhouse are wheelchair accessible.
History and name
The Mandan called the falls Minni-Soze-Tanka-Kun-Ya, "the great falls," and William Clark gave them the English name in 1805. Meriwether Lewis reached them on June 13, 1805, and described them as the grandest sight of his life. The portage route is part of the Great Falls Portage National Historic Landmark, designated in 1966.
Nearby
Upstream on the Missouri, Crooked Falls is about 4.2 miles away, Rainbow Falls about 4.6 miles, Colter Falls about 4.8 miles and Black Eagle Falls about 7.3 miles.
Distances are straight-line.