Originally conceived by William Mulholland and designed by Chief Engineer Frank E. Weymouth of the MWD, it was the largest public works project in southern California during the Great Depression.

On the other side of the mountains the aqueduct continues to run underground until it reaches the terminus at Lake Mathews.

From there, 156 mi (251 km) of distribution lines, along with eight more tunnels, delivers water to member cities.

[3] As the Los Angeles metropolitan area grew in the early 1900s, Mulholland and others began looking for new sources of water.

By the early 1920s, Los Angeles had grown so rapidly that the Owens River watershed could no longer supply the city's needs for domestic and agricultural water.

The plan was to dam the Colorado River and carry its waters across hundreds of miles of mountains and deserts.

In 1924, the first steps were taken to create a metropolitan water district, made up of various cities throughout southern California.

The Metropolitan Water District ("Met") was incorporated on December 6, 1928, and in 1929 took over where Los Angeles had left off, planning for a Colorado River aqueduct.