From the United States Mint website (http://www.usmint.gov):
The primary mission of the U.S. Mint is to produce an adequate volume of circulating coinage for the nation to conduct its trade and commerce. The other major responsibilities of the Mint include: The annual production of 14-20
billion circulating coins. Distributing U.S. coins to the Federal Reserve banks and branches.
Maintaining physical custody and protection of the Nation's $100 billion of U.S. gold and silver assets. Producing proof and uncirculated coins, commemorative coins, and medals for sale to the general public. Manufacturing and selling platinum, gold, and silver bullion coins. Oversight of production facilities in
Denver,
Philadelphia,
San Francisco and
West Point, N.Y., and the
U.S. Bullion Depository at
Ft. Knox, Kentucky. Receiving, redeeming, and processing mutilated coins.