On July 3, 1975, just before the Fourth of July holiday weekend, a summer monsoon triggered a flash flood in the Las Vegas Valley.

On July 3, 1975, raging floodwaters cannonballed down the Flamingo Wash, a major tributary of the valley's natural drainage system, from the Spring Mountains, sweeping hundreds of cars from the Caesars Palace parking lot on the Las Vegas Strip. (Clark County Museum)

On July 3, 1975, floodwaters rampaged through the parking lot at Caesars Palace on the Las Vegas Strip, damaging hundreds of vehicles and sweeping away many more. (Las Vegas Review-Journal File)

On July 3, 1975, the Thursday before the Fourth of July holiday weekend, a summer monsoon triggered a flash flood in the Las Vegas Valley.

While some gamblers sat unaware inside Las Vegas Strip casinos, floodwaters put Interstate 15 exits underwater and closed major intersections.

Raging water swept down the Flamingo Wash into the parking lot at Caesars Palace on the Strip, flooding hundreds of cars. Cranes had to be brought in to move the cars. Some vehicles were reported to be found miles away from Caesars.

Rushing water and erosion brought down telephone poles. Sewage plants were overwhelmed and fetid water was expelled through manhole covers.

Well owners were warned of contamination. Estimates of damage exceeded $4 million.

While directing traffic, two North Las Vegas city employees died after they were hit by a wall of water at Losee and Craig roads and swept away from their vehicle.

In the July 4, 1975, edition of the Review-Journal, a spokesman for the Las Vegas Public Works Department said it was the worst flooding in the area since 1955, which caused an estimated$3 million in damages.

Contact Michael Quine at mquine@reviewjournal.com. Follow @Vegas88s on Twitter.