Born in Borgentreich in Westphalia in 1825, the son of Samuel Mosesand Hanna Rosenbaum, Moses Rosenbaum immigrated to the United Statesat the age of thirteen, settling in San Francisco in 1850. With hisbrother Albert and Joseph Brandenstein, he established a tobaccofirm, A. S. Rosenbaum & Co., at one time the largest in the West.Their business partner would marry the Rosenbaums’ sister Jane, andin 1854 Moses married Bertha Kohlberg with whom he had six children.

Rosenbaumserved as the secretary of the California Republican State CentralCommittee and volunteered as a firefighter with the Howard No. 3 FireCompany. He was philanthropist and active in Jewish organizations inthe city and a member of Temple Emanu-El.