Hammond took his first mining job as a special expert for the US Geological Survey 1879-1880 in Washington, DC. He returned to California in 1881 to work for Senator George Hearst, the mining magnate and father of William Randolph Hearst. In 1882, he was sent to hostile country in Mexico, near Sonora, to become superintendent of Minas Nuevas. When a revolution broken out, Hammond barricaded his family in a small house and fought off the attacking guerrillas.