Mulholland? Sure, you say. I know that name. Isn’t it a twisty street somewhere in Los Angeles, and wasn’t Mulholland Drive the title of an eerie film by David Lynch? And didn’t Roman Polanski and Robert Towne’s movie Chinatown have a character with the sound-alike name of Hollis Mulwray, the L.A. city water engineer who is murdered for refusing to forget the mysterious collapse of something called the Vanderlip Dam and threatening to expose John Huston’s sinister water grab?

In fact, there was a real William Mulholland and his life was the kind Americans admire and mythologize, including humble beginnings, hard work, and mostly self-taught expertise, leading to an unprecedented engineering achievement that launched and sustained the rise of America’s second-largest city, and ending with a fatal disaster considered the worst in 20th-century U.S. history. (When I wrote my new book, Floodpath: The Deadliest Man-Made Disaster of 20th Century America and the Making of Los Angeles, there was no question but that Mulholland would be the narrative’s driving force.)

Born in Ireland in 1855, young Willie Mulholland ran away to sea when he was 15, and in 1877 followed his sense of adventure to Los Angeles, a frontier town with a welcoming climate and a population of a little more than 11,000. The year before, the once isolated Mexican pueblo gained easier access to the rest of the United States with the arrival of the transcontinental railway.

In 1878, at age 22, Mulholland started his life’s work as a ditch digger for the city’s privately managed water distribution system, which was linked to the shallow Los Angeles River. In the years that followed, the Irish immigrant’s no-nonsense attitude and management skills led him to the leadership of a new city-owned water department in 1902. By then, the population of the sunny City of the Angels had boomed to more than 102,000, nearly 10 times what it was when Mulholland rode into town. If the trend continued, it was clear L.A.’s thirst would overwhelm the undependable Los Angeles River. In 1904, anticipating this dire forecast, former mayor Fred Eaton came up with an audacious scheme to import water from the Owens Valley, located more than 200 miles away beneath the snow-covered Eastern Sierra.

Enlisting the secret support of local political and business leaders, without letting Owens Valley farmers and ranchers, or even Angelenos, know what he was up to, Eaton bought the land and water rights needed for an unprecedented 233-mile-long aqueduct, which could use gravity alone to carry a man-made river south. Before plans were public, anticipating a real estate bonanza, insider businessmen led by Harrison Gray Otis, owner of the Los Angeles Times, quietly bought property options in the San Fernando Valley, where the aqueduct was expected to end. Funding for the project came from East Coast investors, and William Mulholland enthusiastically accepted the challenges of design, construction and getting the job done—on time and on or under budget. It would be the longest liquid pipeline in the world—at the time a job compared to the building of the Panama Canal. ...