Nestling along a hillside, among scrub oaks, in a slightly elevated clearing, near the base of Mt. Ophir, Mariposa County, is located Moffat’s Mint. This was built of local slate rock, in 1850, by John L. Moffat, who had been appointed the year previously by President Zachary Taylor as U. S. Assayer for California, at which time, he established an Assay office on Commercial Street, in San Francisco.

Moffat, originally from Brooklyn, New York, was an experienced assayer and geologist and had spent many years in the Georgia gold fields. He had filed a mining claim on Mt. Ophir, which he operated alone at first and then in association with an incorporated company, the Merced Mining Company. It was this mine that supplied the gold used in the first fifty dollar slugs, made by him in his mint at Mt. Ophir and these were the first coins issued in California under Governmental authority. Moffat’s Mint at Mt. Ophir, therefore, was really the Nation’s first authorized private mint.

There were a number of private concerns issuing gold coins at this time, which coins were equal to and in some cases better than, regular United States coins, but they were not legal tender, although accepted as such by the public in its necessity to have a more convenient medium of exchange than gold dust. Moffat, later, made coins of other denominations, but his first issuance were the fifty dollar slugs and they were coined at his Mt. Ophir Mint and were legal tender, being issued under Governmental authority.

The Daily Alta California of February 21, 1851, described the fifty dollar gold pieces, issued in 1851, by Moffat, as follows: “Hexagonal fifty dollar gold pieces, manufactured under an Act of Congress, appointing a U. S. Assay office, in California, and made under the supervision of the U. S. Assayer, were first issued yesterday. These coins are legal tender and the coin of the United States Government to all intents and purposes. The coin contains upon one face an eagle in the center, around which are the words, ‘United States of America’. Just over the eagle is stamped ‘887 thous.’, signifying the fineness of the gold. At the bottom is stamped ‘50 dolls’. The other face is ornamented with a kind of work, technically called ‘engine turning’, being a number of radii, extending from a common center, in which is stamped in small figures ‘50’. Around the edge is stamped the name of the United States Assayer.”

One of California’s very first codes of miners’ customs and usages was framed and adopted by a convention of quartz miners, which convened pursuant to public call, in the town of Quartzburgh, County of Mariposa, on the 25th day of June, 1851. Colonel Thorn was unanimously elected President and J. T. Temple, Secretary, and both signed the adopted rules and regulations; and in addition, pledged their honor and their lives for full and faithful performance.

This code helped to bring order out of chaos and proved an extremely important factor in helping the mining industry of the State. It was the mining law in Mariposa County for many years, without a single change, and was, also, used in many other parts of the State.

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