Arrowrock Dam, Engineering Innovation and Building Block to Boise's Expansion

In 1911, the U.S. Reclamation Service broke ground on the Arrowrock Dam located on the Boise River, 22 miles upstream from Idaho’s capital. Arrowrock Dam was the tallest dam in the world in 1915 when the project was completed. The dam is known as an engineering marvel that is referred as Idaho’s Eight Wonder of the World.

Arrowrock Dam transformed Boise by providing agricultural opportunities and is responsible for the development of Boise. Boise's roots were in the goldfields of surrounding foothills during the mid-nineteenth century. Around the 1860’s the gold rush declined, residents noticed the plentiful valley had an economic opportunity with agriculture, and irrigation became the key of the development. Decades later after numerous ideas and attempts to provide irrigation to the Boise Valley, the newly formed U.S. Reclamation Service engineers came up with the idea of constructing a dam upstream on the Boise River. The dam’s purpose was to store water for crops from June to late September when water became scarce.

The U.S. Reclamation Service could not begin constructing Arrowrock Dam until they built a railway to the construction site. The railroad from Boise to Arrowrock Dam was the first government owned standard gauge common carrier line. Construction on the railway began in August 22, 1910 and was completed in November 1911. On January 16, 1911, work began on the Arrowrock Camp found below the dam. The camp functioned similar to a small town with an estimated thirty buildings. The highest population of the camp was 1400 people, however the camp did not only have men, roughly 200 families also lived within the camp.

Before construction on the dam could begin, the next step in the building process is a diversion tunnel through the side of a hill estimated 470 feet long. After the diversion tunnel completed, the excavation began in February 1912 and the first cement pour was in November 1912.

The Arrowrock Dam is considered the grandfather of many famous dams for example, the Hoover and Shasta Dam. The Hoover and Shasta Dam’s built with the same system engineer Frank Crowe developed the Crowe Cable System. The system used to pour concert and move material due to the height of the dam and move it a long distance a pour concert in a key point. The dam revolutionized the way dams were constructed with similar techniques as well as similar design and models. The construction of the Arrowrock Dam had a large process including a railroad to the construction site, camp building for workers and their families, and finally the dam construction. The Arrowrock Dam has been called Idaho’s Eight Wonder of the World because of the unique the construction process, the size, and aesthetic appearance.


Arrowrock Dam completion
Arrowrock Dam completion Engineers examining the completion of their masterpiece, the Arrowrock Dam. Source:
Beginning of Excavation
Beginning of Excavation The Crowe Crane System used in the beginning of the excavation of the Arrowrock Dam. Source:
Driveway across Arrowrock Dam
Driveway across Arrowrock Dam This is the driveway acroos the peak of the Arrowrock Dam Source:
Small Town at Arrowrock
Small Town at Arrowrock Small town below Arrowrock Dam where the crew and families lived. Source:



Luke Hyde, University of Idaho, “Arrowrock Dam, Engineering Innovation and Building Block to Boise's Expansion,” Intermountain Histories, accessed May 18, 2024,