Chaco Cliffs

The uranium in the panel's list came out of the ground a few miles north of here, and in 1979 some of it came back down the Puerco. At about 5:30 on the morning of July 16, the tailings dam at United Nuclear's Church Rock mill broke, sending some 1,100 tons of tailings and about 94 million gallons of acidic, radioactive water down Pipeline Arroyo and through Navajo grazing land. It came fourteen weeks after Three Mile Island and remains the largest release of radioactivity in the country's history. The mill closed in 1982.

What the plaque says

Official Scenic Historic Marker Chaco Cliffs Great cliffs of red sandstone form the southern boundary of the San Juan basin. The strata exposed here are the gently upturned edge of the structural basin which contains coal, uranium, oil and gas resources. The Zuñi Mountains to the south represent the old basement rock upon which the basin strata were deposited. Elevation is 6,900 feet.

Where it stands

Worth the stop nearby

• Window Rock — 27 mi
  Tségháhoodzání — the sacred arch, and the capital of the Diné

More markers nearby

• Gallup — 3.7 mi
• Fort Wingate — 5.5 mi
• Emma Estrada (1933-1997) / Parteras of New Mexico — 6.9 mi
• Continental Divide — 18 mi