Great Falls in Cascade County, Montana — The American West (Mountains)

It's All Geometry

Photographed By Barry Swackhamer, August 16, 2022

1. It's All Geometry Marker

Captions: The Great Falls during high water season; (lower right) Sextant; Clark's drawing of the falls.

Inscription. "...and took the hight with as much accuricy as possible with a Spirit Leavels &c. dined at a fine Spring 200 yards below the pitch near which place ₄ Cotton willow trees grew. on one of them I marked my name the date and the hight of the falls," -- Captain William Clark June 17, 1805

After Captain Lewis arrived at the Great Falls, it was now Captain William Clark's job to measure and map them. Captain Clark, using a sextant and a rod, employed geometry to measure the falls. Using surveyor's tools, Clark measured the falls to be a height of 97 feet and 1/4 inches.
Clark's measurements were remarkably accurate. Recent electronic measurements record the height of the falls as 96 feet. Clark was off by a mere 1 foot 1/4 inches!

Erected by North Western Power.

Topics and series. This historical marker is listed in this topic list: Exploration. In addition, it is included in the Lewis & Clark Expedition series list.

Location. 47° 34.119′ N, 111° 7.227′ W. Marker is in Great Falls, Montana, in Cascade County. Marker can be reached from Ryan Dam Road. The marker is located on Ryan Island, accessed by a suspension bridge. Touch for map. Marker is at or near this postal address: 160 Ryan Dam Road, Great Falls MT 59404, United States of America. Touch for directions.

Other nearby markers. At

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least 8 other markers are within 6 miles of this marker, measured as the crow flies. From Water Comes Power (here, next to this marker); Rocks of the Gorge and Falls (a few steps from this marker); Formation of the Gorge and Falls (within shouting distance of this marker); The Falls Undergo a Change (within shouting distance of this marker); Captain Lewis Arrives at the Great Falls (within shouting distance of this marker); Great Falls of the Missouri River (about 700 feet away, measured in a direct line); Lewis and Clark Passed Here (approx. 0.2 miles away); The Smallest River Runs Through It (approx. 5.6 miles away). Touch for a list and map of all markers in Great Falls.

Photographed By Barry Swackhamer, August 16, 2022

2. It's All Geometry Marker

Great Falls of the Missouri before the construction of Ryan Dam image. Click for full size.

Photographed By M.L. DeLong

3. Great Falls of the Missouri before the construction of Ryan Dam

Credits. This page was last revised on May 2, 2024. It was originally submitted on May 2, 2024, by Barry Swackhamer of Brentwood, California. This page has been viewed 48 times since then. Photos: 1, 2, 3. submitted on May 2, 2024, by Barry Swackhamer of Brentwood, California.