Historic American Engineering Record: Horseshoe Dam

Historic American Engineering Record (HAER) No. AZ-24 presents a written historical summary and relevant historical documentation about the construction and use of Horseshoe Mesa Dam, which impounds the Verde River 66 miles northeast of Phoenix, Arizona to create Horseshoe Reservoir. The report contains a narrative description, photographs, drawings, and maps.

Horseshoe Dam is located at a topographical bend in the Verde River about forty miles north of the confluence of the Verde with the Salt River. Its name probably derives from the distinctive shape formed by the riverbed in curving around a large rock formation. Draining an extensive portion of central Arizona, the Verde River flows southward from headwaters in the San Francisco Mountains before entering into the Salt River about 40 miles east (upstream) of Phoenix.

The dam is a major component of the Salt River Project's Water supply system. It was completed between 1945 and 1946 as part of the industrial production effort for strategic materials in World War II. Although administered by the Salt River Valley Water Users' Association, the dam's construction was funded by the Phelps Dodge Copper Company and the U.S. Defense Plant Corporation. It functioned as a means to increase the Phoenix region's water supply in exchange for water delivered to the Morenci copper mine in eastern Arizona. The structure is technologically significant as the first major earth and rockfill dam built as part of the Salt River Project.

Horseshoe Dam lacks a hydroelectric powerhouse or other power production facilities. Since the dam's completion, no serious consideration has been given to outfitting the site with electric generating equipment. Water releases from Horseshoe Reservoir have always been controlled exclusively by the needs of water users in the Salt River Valley without consideration given to potential hydroelectric power generation.

The dam's chronology divides into two distinct phases. The first involves the initial discovery of the Horseshoe site at the end of the 19th century and the the Rio Verde Canal Company's plans to develop the "Paradise Valley'' north of present-day Scottsdale with irrigated agriculture. The second phase concerns the activities of the Salt River Valley Water Users' Association to develop the resources of the Salt River for the benefit of the farmers in the greater Phoenix area. The Rio Verde Canal Company's efforts to develop Paradise Valley were at odds with the Salt River Valley Water User's Association mission to incorporate the flow of the Verde into that of the Salt for use in the central valley. The struggle over the Verde River's water formed a compelling background for Horseshoe Dam.