The National Priorities List (NPL) is the list of national priorities among the known releases or threatened releases of hazardous substances, pollutants, or contaminants throughout the United States and its territories. The NPL is intended primarily to guide the EPA in determining which sites warrant further investigation.

In the case of the Butte area of western Montana, all associated sites are on the National Priority List, with the exception of the mainstem Clark Fork River. Many sites in the region have been listed on the NPL since 1982.

For more information, visit the EPA National Priority List website.