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The Hoover Dam is 75 years old

The Las Vegas Review-Journal has a good article on the opening of the Hoover dam in 1935, and its continuing impact on life in Southern Nevada and a vast swathe of the American West that depends on the dam for power and water:

A river that once shrank to a shallow stream during severe dry spells now runs reliably to taps in Los Angeles, San Diego, Phoenix and Tucson, four of the nation's fastest growing cities of the last 30 years.

A river that once raged with damaging floods powerful enough to refill California's ancient, inland Salton Sea now supplies a nation with vegetables grown in the dead of winter in the continent's harshest desert.

"Everything south of Hoover is possible because of Hoover," Mulroy said.

Without it, she said, "there wouldn't be a modern West."

Two years ago I had the privilege of flying over the dam in a helicopter. The scale of the construction and of Lake Mead, in the context of massive natural formations, was truly astounding from that vantage point. But I also remember the pilot pointing out high-water marks well above the water level, noting how much lower the reservoir was compared to its historical average and the real risk that drought, demands on the water supply and the silt building up behind the dam could threaten this marvel of engineering and the communities that depend on it.

The New York Times had an excellent roundup of those issues the other day, titled "Water Use in Southwest Heads for a Day of Reckoning":

The impact of the declining water level is visible in the alkaline bathtub rings on the reservoir's walls and the warning lights for mariners high on its rocky outcroppings. National Park Service employees have repeatedly moved marinas, chasing the receding waterline.

Adding to water managers' unease, scientists predict that prolonged droughts will be more frequent in decades to come as the Southwest's climate warms. As Lake Mead's level drops, Hoover Dam's capacity to generate electricity, which, like the Colorado River water, is sent around the Southwest, diminishes with it. If Lake Mead levels fall to 1,050 feet, it may be impossible to use the dam's turbines, and the flow of electricity could cease.

The fretting that dominates today's discussions about the river contrasts with the old-style optimism about the Colorado's plenitude that has usually prevailed since Hoover Dam — then called Boulder Dam — was completed 75 years ago, impounding the water from Lake Mead.

The article also features a picture of those "bathtub rings," complete with a jet skier, by photographer Jim Wilson.

The historical pictures above, by famed LIFE Magazine photographer Alfred Eisenstaedt, are from a gallery of 30 images published by LIFE.com in July. The slideshow provides a good historical overview of the dam and is well worth a look, particularly in light of the dam's continuing importance to millions of Americans.

LIFE.com does a great job of bringing significant pictures from their rich archives to light for the first time.They feature photographs by Eisenstaedt in a number of galleries.

Follow us on Twitter via @msnbc_pictures. Follow our friends at LIFE.com via @LIFE. To learn more about the business of water, and some threats to our water supply, watch CNBC's documentary Liquid Assets, which airs tonight for the first time at 9 p.m. ET.