10 Dollars - Clark, Gruber & Co.

Clark, Gruber & Co. was a Denver banking firm that began striking its own gold coinage in 1860 when the nearest U.S. Mint was in New Orleans — effectively useless to Colorado Territory miners hauling raw gold dust. The federal government tolerated the private issue because the alternative was worse: a chaotic barter economy running on unweighed, unassayed dust. Congress authorized the Denver Mint in 1862 partly as a direct response to Clark Gruber's operation, which had demonstrated that the demand was real and the volume substantial.

The firm was purchased outright by the Treasury in 1863 and converted into an assay office rather than a coinage facility — a bureaucratic decision that frustrated Colorado miners for years afterward.