The U.S. Mint Coins:
The Denver Mint is the only U.S. Mint whose origins can be traced back to the government buying out a private competitor in the coinage business. The Colorado Gold Rush, also known as the Pike’s Peak Gold Rush, began in 1858. Millions of dollars worth of gold nuggets and dust flowed into the newly-founded city of Denver, and calls began for a U.S. Mint branch there, as had been done for Charlotte, Dahlonega, and San Francisco. The Treasury department refused, saying that the badlands and hostile Indian territory between Colorado and the East Coast made establishing a Mint in Denver too dangerous.
Where the government fears to tread, private enterprise often steps in. Three businessmen named Austin Clark, Milton Clark, and Emmanuel Gruber opened a combination bank, assay office and mint called Clark, Gruber & Co. in Denver in 1860, as a result of the severe shortage of money in the area. They immediately began striking gold coins with same denominations as U.S. gold coins, but with their company name on them (and more gold per coin than the U.S. coins!) This came to a halt when the Federal government noticed the large amount of gold dust they were sending to the Philadelphia Mint, and learned of their popular private gold coins. The government bought out the company’s assaying and minting operations, and shut the mint down.
The Gruber building was turned into a U.S. Assay Office, tasked with refining and sending gold and silver bars to the Philadelphia Mint. By the 1890s, the Denver Assay Office was sending over $5 million of bullion back East every year, and the tiny building was in a decrepit state. Congress authorized the Denver Mint in 1895, and construction began two years later. Budget shortages delayed the completion of the facility and it wasn't until 1904 that the Denver Assay Office moved into the new building. The minting equipment wasn't installed and ready until 1906. The Denver Mint is the only U.S. Mint besides the "mother mint" in Philadelphia that produces circulating coins. It also produces commemorative clad coins. The Denver Mint is open for tours Monday through Thursdays (reservations required.)
The Denver Mint uses the “D” mint mark. Though the old Dahlonega Mint (1838-1861) also used the “D” mint mark, the coin types minted in Dahlonega had long been replaced by the time the Denver Mint opened, so the mint mark was re-used.