Brannon started life in Saco, Maine, in 1819 before moving with his family to Ohio when he was 14 years old. He became a printer’s apprentice and, in 1836, began to move around as a journeyman printer. Converting to Mormonism in 1842, he moved to New York City to help publish several Mormon newspapers. Three years later, Brannan led a group of over 200 New York Mormons to California to find a better life. Briefly, he published a San Francisco newspaper before moving on to John Sutter’s settlement, where he opened a general store. Soon, however, the Mormons accused him of diverting Mormon funds into his own business and expelled him from the church.
When James Marshall discovered gold in 1848, Brannan capitalized on it by widely publicizing the discovery and outfitting the flood of prospectors. Before long, he became the Golden State’s first millionaire. The following year, he returned to San Francisco, where he was elected to the City Council and played a leading role in organizing the controversial Committee of Vigilance. His wealth grew in various business ventures, including land investments, banking, and railroad and telegraph companies. However, Brannan was a serious drinker, ultimately leading to his loss of fortune and his death in 1889.