Columbia-Pacific Northwest Region

Cultural History

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Arrowrock Dam has been a cornerstone of development in Idaho’s Treasure Valley, providing irrigation water to farmers and flood control on the lower Boise River for 100 years. It was built by the United States Reclamation Service (now known as the Bureau of Reclamation). It is located about 20 miles east of Boise, Idaho. Arrowrock was built for the Arrowrock Division of Reclamation’s Boise Project which provides water to 397,000 acres in Idaho and Oregon. The Boise Project stretches from Boise, Idaho to Nyssa, Oregon. There are two divisions with the Boise Project, the Arrowrock Division and the Payette Division.

Arrowrock cost $4,796,488.82 to build, which was $2 million under budget.

Construction began in 1911. Cableway systems were used to move the concrete to build the dam. A powerplant housing three 500-kilowatt hydroelectric generating units was added to Boise River Diversion Dam, which is located 14 miles downstream, to furnish electric power for the construction of Arrowrock Dam.

The Boise & Arrowrock Railroad was the first government owned standard gauge common carrier railroad. The railroad was 17 miles long and extended from the construction camp (referred to as Arrowrock City) to Barber Junction just northeast of Boise. The trains transported supplies, workers and visitors to the dam site.

The dam was officially dedicated Oct. 4, 1915, with approximately 5,000 people in attendance. Construction was completed in November and it was the tallest dam in the world until 1925.

Arrowrock Dam was listed on the National Register of Historic Places in 1976 to identify, evaluate and protect America’s historic and archeological resources which are associated with the structure.

Since the beginning of the operations, Arrowrock Dam played a major role in the agricultural development of the Boise Valley throughout the 20th century, and continues to provide irrigation, recreational, fish and wildlife and flood control benefits. The 100th anniversary of the completion of Arrowrock Dam is in Nov.