Introduction to the U.S. National Mint: This is the branch of the U.S. National Mint in Denver. It is mainly responsible for minting coins for circulation and some commemorative coins. The Denver Mint was formerly the place where gold was officially inspected and opened in 1863, five years after the local gold mine was discovered. At the beginning of the 20th century, a total of $5 million worth of gold and silver was processed annually. In 1906, the Mint established a Mint Branch there, marked D.