Opened 110 years ago in 1915, it is located on the border of Boise and Elmore counties, upstream of the Lucky Peak Dam and reservoir.

The spillway elevation for Arrowrock is 3,219 feet (981 m) above sea level and its primary purpose is to provide irrigation water for agriculture.

As the structure was some twenty miles (32 km) upstream from the Boise River Diversion Dam, routing supplies to the worksite would be a massive undertaking unto itself.

The Reclamation Service elected to construct a new rail line on the old wagon road leading north to Idaho City.

However, when the Oregon Shortline refused to honor the pact between Barberton and Reclamation, the Arrowrock & Boise terminal was reduced to a field just outside the Barber lumberyard.

Although the construction was delayed several times by the shortage of railroad ties, workers finished the track in early November.

Not only was the site fully powered, but also it provided a central heating plant, running water and an efficient sewage system.

Finished in 1912, the plant's three generators produced 1,500 kilowatts of electricity for Arrowrock's camp, sawmills, and giant cement mixers.

The original governors, slate control panels, transformers, overhead crane, and generator housings, although no longer functional, were retained for historic purposes.

As labor was becoming more plentiful with the completion of Deer Flat and the Diversion Dam, wage rates began to decrease.

As stated above, the workers set several construction records, not the least of which included the 527,300 cubic yards (403,100 m3) of concrete laid on the dam.

Along with the refurbished 70-ton Atlantic steam shovel from Deer Flat were two versatile 18-ton "dinkey" excavators and several brand new dump cars.

Additionally, one Buick and seven Ford trucks serviced both crews and visitors and provided an unexpected level of mobility throughout the campsite.

In addition, engineers pioneered the use of dam instrumentation with the placement of ten thermometers embedded deep within the structure's concrete.

Along with innovative contraction joints, the Reclamation Service was able to control the temperature of the setting concrete, ensuring the dams strength.