With more than 150 gold mines, Nevada is the hub of the U.S. gold mining industry, accounting for the most exploration and mining activity on federal lands. The State of Nevada alone annually contributes approximately 75% to national U.S. gold production. States that currently use cyanide leaching to recover metals from ore are: Arizona, California, Colorado, Idaho, Montana, Nevada, Utah, South Carolina, South Dakota and Washington.

http://www.e-mj.com/index.php/features/1656-the-current-status-of-cyanide-regulations