The Colorado River bobs and jukes through the crisp sandstone of the western high plains. Earliest explorers saw it as a defining characteristic of Arizona and much of the semi-arid western United States. Today, the river is a monument to American riverine technology, as aqueducts and hydroelectric dams use the Colorado to make the American West a hydraulic society. The first of the incursions into the river is also the most famous: Hoover Dam.

Opened in 1935, Hoover Dam stands as a larger-than-life symbol of fluctuating meaning for generations of Americans. Even without such symbolic significance, the dam remains among the nation's most impressive engineering achievements.

A major part of the dam's significance derives from the structure itself. The dam, which has long-since repaid the $165 million cost for construction, is a National Historic Landmark and has been rated by the American Society of Civil Engineers as one...