There are more ways than ever to listen to History Daily ad free.

Listen with Wundry Plus in the Wundry app.

As a member of Noiser Plus at Noiser.com or in Apple Podcasts,

or you can get all of History Daily plus other fantastic history podcasts at into History.com. It's December 20th, 1921, on the Colorado River, the border between Nevada and Arizona.

A small flat barge rocks in the churning waters as it heads downstream.

Among the men clinging to its wooden sides is John Gregory Tierney, a 36-year-old surveyor. John struggles to keep his balance as the river surges through canyons of orange rock.

He's surprised that the water levels are this high.

It hasn't rained in the region for days, and the land beyond the towering banks of the river is dry and dusty swath of the American Southwest.

In fact, a need for irrigation is partly what brings John and his crew to this area.

They're searching for the perfect spot to build a dam. what brings John and his crew to this area.

They're searching for the perfect spot to build a dam, one which will control the flow of the Colorado River,

providing hydroelectric power and irrigation for farming and limiting the river's perilous floods.

John believes they're nearing the ideal site,

a place where the narrow river widens into a canyon.

It was once known as Devil's Gate and John can see why.

The Black Mountains loom menacingly over the water on either side,

casting deep shadows over the barge.

John manages to resist the current long enough to moor his boat at the river site.

He hopes to set up camp nearby so his team can survey the area.

But suddenly, the river's roar grows louder.

John looks upstream and sees a rush of water surging toward them.

It must be a flash flood.

...