MK Tunnels in Orangeville, Utah

During the height of the Cold War arms race in the early nineteen-fifties, the U.S. government faced a problem: how to protect command centers from nuclear attack. The answer seemed obvious—go underground. But how deep, and in what kind of rock? According to Atlas Obscura, a contractor called Morrison-Knudsen conducted a series of classified experiments near Orangeville, Utah, to find out. They carved horizontal tunnels into Navajo Sandstone, then detonated explosions of varying sizes above them while instruments inside measured the blast effects. Though the work was officially secret, Morrison-Knudsen was surprisingly open about it—even announcing tests beforehand, and local residents photographed the blasts. The experiments ran until nineteen fifty-two, when the data revealed an inconvenient truth: Navajo Sandstone simply wasn't suitable for hardened bunkers. The lessons learned pointed the military toward a different solution: constructing their underground command center in Cheyenne Mountain instead.

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