People have lived in the San Fernando Valley for thousands of years. The Tongva, Tataviam, and Chumash people lived inhabited the place long before the Spanish arrived in the 18th century and built the Mission San Fernando. Mexicans established ranchos there in the 19th century, and the white Lankershims and Van Nuyses arrived in the 1870s.
But the great, suburban Valley we know today officially began on March 29, 1915, when 681 residents voted to join the city of Los Angeles (25 people voted against).
Valley scholar Kevin Roderick describes the enormity of the addition: “In one stroke, Los Angeles more than doubled in size. The San Fernando Valley is large enough to hold all of Boston, San Francisco and Washington D.C.”
Los Angeles got all that land and the Valley got access to the sweet water of the Los Angeles Aqueduct, which had opened in fall of 1913.
The circumstances surrounding the Valley's annexation are slightly less scandalous than Chinatown would lead you to believe (the movie is also set much later), but the broad strokes are not so far off.
Before the aqueduct arrived (and in some cases before it was announced), some of LA’s richest and most powerful men bought up the still-dusty San Fernando Valley at bargain prices, then divided it up into new towns and sold it off with the promise that water would be arriving soon.
Major players in the speculative land grab included Moses Hazeltine Sherman, who also happened to be a water commissioner, and Harrison Gray Otis, the publisher of the Los Angeles Times, who used his paper to hype the Valley’s future.
And while the Los Angeles Aqueduct gave Los Angeles far more water than it could use (squeezing the Owens Valley dry in the process), it couldn't sell the water to anyone outside the city limits.
Here's Roderick in his book San Fernando Valley: America's Suburb:
[T]he city's biggest powers had another idea. They put it in the form of an ultimatum to the Valley: agree to be annexed by Los Angeles or stay dry. Some Valley ranchers with good wells resisted, preferring independence. Voters in Burbank, San Fernando and, initially, Owensmouth and Lankershim declined to be annexed. But on March 29, 1915 … some 170 square miles of the old range that belonged to Pio and Andres Pico became part of Los Angeles. The newly annexed section, including Mission San Fernando Rey itself, more than doubled the city limits.
And with that, here’s a look back at the San Fernando Valley as it was before 1915—before it became the epicenter of sprawl and malls and backyard pools filled with blue water: