Austin Clark and his brother, Milton owned a successful wholesale dry goods business in Leavenworth, Kansas selling commodities such as sugar, tobacco, tea, fish and corn to the local population and to nearby Fort Leavenworth.

In January 1858 the Colorado gold rush brought great demand for goods such as were sold by the Clarks. That March, the brothers decided to form a banking business partnership with Emanuel Gruber, also of Leavenworth.

Clark, Gruber & Co. prospered from the start. Heavy trade in gold dust at both the bank and their wholesale operations created a need for a branch bank and mint in Colorado near the source of the gold. It was not cost effective for the firm to ship gold dust to Philadelphia and wait sometimes up to three months for their funds.

The Clark, Gruber & Co. Bank and Mint opened in Denver, Colorado on July 20, 1860. By October, the gold coins of Clark, Gruber & Co. had become the principal currency of Colorado. The coins were well made and of proper weight and fineness.