The Department of the Interior (DOI) is the nation's principal conservation agency. Its mission is to protect America's natural resources, offer recreation opportunities, conduct scientific research, conserve and protect fish and wildlife, and honor our trust responsibilities to American Indians, Alaskan Natives, and our responsibilities to island communities.

DOI manages 500 million acres of surface land, or about one-fifth of the land in the United States, and manages hundreds of dams and reservoirs. Agencies within the DOI include the Bureau of Indian Affairs, the Minerals Management Service, and the U.S. Geological Survey. The DOI manages the national parks and is tasked with protecting endangered species.

The Secretary of the Interior oversees about 70,000 employees and 200,000 volunteers on a budget of approximately $16 billion. Every year it raises billions in revenue from energy, mineral, grazing, and timber leases, as well as recreational permits and land sales.