Crocker was born into a modest upstate New York family in 1822. When he was fourteen, the family moved west to a farm in Iowa. Crocker soon became independent, working on several farms, a sawmill, and at an iron forge. In 1845 he founded a small, independent forge.
When news of the fortunes to be made in California spread across the nation, Crocker led a party of Forty-niners overland to the Pacific coast, arriving in 1850. Two years in the mines convinced him that mining was no way to make a fortune, and so he opened a store in Sacramento. By 1854 he was one of the wealthiest men in town and had a strong business relationship with Mark Hopkins, Collis Huntington and Leland Stanford, who together with Crocker came to be known as "The Big Four" for their prominence in California's stunningly rapid economic development.
One of the Big Four.