Lake Mead, straddling the border of Nevada and Arizona, is the largest man-made reservoir in the United States by water capacity. Located just east of Las Vegas, this immense lake is a dramatic contrast to the surrounding desert landscape. It is not a natural formation but the direct result of a monumental civil engineering effort designed to harness the power of the Colorado River.
The Need for Water Control in the Southwest
The need for a massive water storage facility was driven by the challenges presented by the Colorado River in the early 20th century. The river followed an unpredictable cycle, prone to destructive spring flooding that devastated farmland, such as California’s Imperial Valley. For example, between 1905 and 1907, the river inundated over 100,000 acres of fertile land. Controlling this chaotic flow was necessary, as was securing a steady water supply for the rapidly expanding cities and agricultural areas of the Southwest. This necessity led to the 1922 Colorado River Compact, which allocated water rights among the seven basin states and provided the legal framework for the construction project.
Building the Hoover Dam
The reservoir’s creation began with the authorization of the project through the Boulder Canyon Project Act of 1928, which provided financial backing. Construction spanned from 1931 to 1936 and first required diverting the powerful Colorado River away from the Black Canyon site. Crews blasted and excavated four massive tunnels, each 56 feet in diameter, through the solid rock walls—two on the Nevada side and two on the Arizona side. After the river was routed through these temporary tunnels in November 1932, workers began clearing the canyon floor to pour the foundation for the concrete arch-gravity dam. The finished structure stands 726 feet high, acting as the barrier that would hold back the river’s flow and form the lake.
The Process of Filling Lake Mead
As the dam neared completion, the final step was blocking the river’s path to allow water to accumulate. This process began in February 1935 when a steel gate was lowered, sealing the entrance to one of the diversion tunnels. The Colorado River was forced to back up into the steep-walled canyons, transforming the dry landscape into a deep reservoir. The lake accumulated water over several years, not reaching its designated capacity until 1941, seven years after filling started. The reservoir was officially named Lake Mead, honoring Elwood Mead, who served as the Commissioner of the U.S. Bureau of Reclamation during the project’s planning and initial construction.