HOOVER DAM: On this day in 1935, Hoover Dam was officially dedicated. At the time, it was the most expensive public works project in American history. Today it continues to supply power for over a million homes (and reliable water too). I am told my house in San Diego is usually one of them.

Just starting on this epic undertaking required building a railroad from Las Vegas to the site, constructing an entire town—Boulder City—to house the workers, and temporarily diverting the Colorado River through four diversion tunnels. All of this had to be done in a place where summer temperatures frequently top 110 degrees.

Among the many thousands of workers were the so-called “high scalers”—some of whom had been circus acrobats. Their job was to climb down the canyon walls on ropes and remove all loose rock in preparation for building the actual dam. Jackhammers and dynamite were their tools.

The U.S. Bureau of Reclamation web site tells this story:

Perhaps the most famous feat any of the high scalers ever performed was a daring midair rescue. Burl R. Rutledge, a Bureau of Reclamation engineer, fell from the canyon rim. Twenty-five feet below, high scaler Oliver Cowan heard Rutledge slip. Without a moment’s hesitation, he swung himself out and seized Rutledge’s leg. A few seconds later, high scaler Arnold Parks swung over and pinned Rutledge’s body to the canyon wall. The scalers held Rutledge until a line was dropped and secured around him and the shaken engineer was pulled, unharmed, to safety.

I know I’ll forget by tomorrow, because it’s the 21st century and it’s hard not to take electrical power for granted. But today at least I’m going to try to remember all those who worked on the dam—including the hundred or so who died—when I flip on a switch and a light comes on. It’s a tribute to how lucky I am that I am likely to forget even before lunchtime.