The United States Mint at Denver was established by Congress in 1862 as a branch mint. One year later, the facility opened an assay office to meet the needs of miners flocking to the city during Colorado’s gold rush. Congress converted the facility into an official Mint in 1895 and production of gold and silver coins began in 1906. Since then, each coin struck at the Denver Mint, including circulating coins and annual uncirculated coin sets as well as some our most beloved commemorative coins, bears a small, capital letter “D” on its obverse, or “heads,” side.