When the War of the Pacific broke out between Chile and the united forces of Bolivia and Peru, his family moved to Oakland, California, the state where his father had resided previously and retained business interests. They soon moved to Tucson, Arizona. In 1880, his father opened the Jacobs Assay Office (still in operation by his descendants). During the 1880s through the 1890s, Washington M. Jacobs managed varied mining interests, and was elected Justice of the Peace of the Tucson Precinct of Pima County in 1887, serving for two years. Benjamin Jacobs grew up in multi-cultural Tucson and learned the basics of chemistry in his father's assay and chemical laboratory. He also worked in the family mining businesses in Arizona and Mexico, one of which at Ajo, Arizona later became a major copper producer. After his father's death in 1899, Benjamin Jacobs relocated his mother and younger sisters to Oakland, where nearby, he attended and briefly taught chemistry at the University of California, Berkeley.