Other gold and silver discoveries in the West, particularly in Nevada and Colorado, triggered the need for additional Mints. The private Clark, Gruber and Co. Mint in Denver was purchased by the Federal government in 1863 and extensively remodeled. Although officially designated a Branch Mint, it served instead as an Assay Office, weighing and analyzing the purity of precious metals brought to its front doors, and producing bars and ingots. A new Mint was built in Denver at the turn of the century, opening for coining in 1906. Denver has struck coins of all alloys: copper, copper-nickel, silver and gold.
The Carson City Mint in Nevada opened in 1870 and closed in 1893. Carson City struck silver and gold coins only.
The San Francisco Mint closed after striking 1955 coinage; its presses were no longer needed to keep up with the national demand for coinage. Congress revised its status in 1962, naming it the San Francisco Assay Office. However, a coin shortage struck the country and in 1965 the Assay Office resumed striking coins. The facility regained Mint status in 1988.
Currently, there are four federal Mints in operation in the United States.
The Philadelphia Mint (in its fourth building) strikes all denominations of coins for circulation and some collectors' coins. All of the United States Mint's engraving staff work there. However, die production is no longer exclusive to the Philadelphia Mint. In May 1996, a second die production facility was added at the Denver Mint to meet the ever-pressing demand for coinage dies to produce circulating coins for commerce and specially struck coins for collectors.
The Denver Mint is in its original 1906 building, although there have been recent additions; it, too, strikes a combination of circulation issues and collectors' coins.
The San Francisco Mint is in its third building, opened in 1937; today, it strikes coins for collectors only, although in recent years, it also was called upon to strike coins for circulation.
The West Point Mint is the newest facility, having gained Mint status in early 1988; previously, it had been the West PointBullion Depository (opening in 1938) although its coining facilities have been used since 1974. West Point is currently used only for collectors' programs and bullion coins although it has struck coins for circulation in the recent past.