William S. O'Brien

William Shoney O'Brien
Born	1825 Abbeyleix, Ireland
Died	May 2, 1878 (aged 52–53) San Rafael, California
Cause of death	Bright's disease
Resting place	Holy Cross Cemetery, Colma (reinterred from San Francisco's Calvary Cemetery)
Nationality	American
Occupation	Saloonkeeper, stockbrocker, partner in mines
Organization	Flood & O'Brien Consolidated Virginia Mining Company Bank of Nevada
Known for	Being one of the "Bonanza Kings"
Net worth	USD $12 million at the time of his death (approximately 1/696 of US GNP)

William S. O'Brien (1825 – May 2, 1878) was an American businessman who formed a business partnership with fellow Irishmen James Graham Fair, James C. Flood, and John William Mackay, the Consolidated Virginia Mining Company. The four dealt in mining stocks and operated silver mines on the , and in 1873 discovered the great orebody known as the "Big Bonanza" in the Consolidated Virginia and California Mine, an orebody more than 1,200 feet deep, which yielded in March of that year as much as $632 per ton, and in 1877 nearly $190,000,000 altogether. The four-way partnership, although formally called "Flood and O'Brien," was more commonly known as the Bonanza firm. Together they also established the Bank of Nevada in San Francisco, California.

He is considered to have been one of the 100 wealthiest Americans, having left an enormous fortune.

William S. O'Brien at Find a Grave

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Wikipedia