On January 11, 1916, sixteen ASARCO employees were killed and mutilated by Pancho Villa's men near the town of Santa Isabel, Chihuahua. It was one of the incidents that sparked the Mexican Expedition, a United States Army attempt to capture or kill Villa.
Based in Tucson, Arizona, the company grew to conduct mining, smelting, and refining of primarily copper. Open-pit mining is primarily utilized as the most efficient method of recovering this metal; the company's three largest such works are the Mission, Silver Bell, and the Ray mines in Arizona. The company had also operated in silver mining in Idaho. Its mines produce 350,000,000 to 400,000,000 pounds of copper a year.