O'Brien, William Shoney (1825–78), capitalist in America, was born in Abbeyleix, Queen's Co. (Laois). He emigrated to the US as a teenager and settled in New York City, where he became an American citizen on 3 November 1845. Harbouring dreams of finding adventure in Texas, he worked as a grocery clerk and waited for an opportunity to present itself. In 1849 gold was discovered in California and O'Brien was one of the original ‘forty-niners’ who set out to make their fortune. He arrived in San Francisco on 6 July, and worked at various jobs until he had raised enough money to begin prospecting. While mining at Poor Man's Gulch on Feather River (1850), O'Brien met James Clair Flood, a fellow Irishman, who was later to become his business partner. Forced to return to San Francisco in 1851, he began working for a ship chandlering company, and became a partner three years later.
A chance encounter with Flood led to their setting up the Auction Lunch Saloon on Washington St., and they used this venue to make important contacts and discover valuable information about mining. Armed with this knowledge O'Brien became a successful stockbroker and invested in several mines at Grass Valley. The income from these ventures was large, and the men sold their saloon in 1866 to concentrate on their investments. Joining forces with two more Irishmen, John W. MacKay (qv) and James G. Fair (qv), O'Brien and Flood invested heavily in various mines on the Comstock Lode in Nevada in the 1860s and waited for a major find. In 1874 the ‘Big Bonanza’ was discovered, making the four men ‘the plutocratic kings of silver-mad Nevada’ (Furnas, 376). An overnight millionaire, O'Brien joined with his partners to form the Nevada Bank of San Francisco in 1875. Within three years he had built a massive fortune, estimated at between fifteen and twenty million dollars. Known as ‘the jolly millionaire’, he did not live to enjoy his good fortune; he contracted Bright's disease and died 2 May 1878. He left his estate to his two sisters and their children, with a legacy for various charities.