In the Oquirrh Mountains, the Bingham Canyon Mine, which contains vast deposits of copper and silver, was developed as the most productive of the county's mines. The mine, located in the southwest portion of the county, attracted thousands of workers to the narrow canyon. At its peak, the city of Bingham Canyon contained 20,000 residents, all crowded along the steep walls of the canyon, and natural disasters were a frequent occurrence. By the early 20th century, most of the mines in the county had closed. However, the Bingham Canyon Mine kept on expanding. In the early 21st century, it is among the largest open-pit mines in the world.