The California Medical Association has its roots in the American Medical Association, founded in 1846, and in the California State Medical Society, which was founded in 1856 by members of the Sacramento Medical Society and the San Francisco County Medico-Chirurgical Society. From the beginning, this first state medical society reflected polarities between the northern and southern sections of the state, and feuding among --and sometimes within --various city and county medical societies. Within a few years personal animosities and petty squabbles had reduced the California State Medical Society to an organization that existed on paper only. Although officers were elected as late as 1860, factional differences around the issues of the Civil War ensured that the California State Medical Society simply did not exist between 1860 and 1870.

In anticipation of the American Medical Association's scheduled meeting at San Francisco in 1871, the California State Medical Society was reorganized in October of 1870. The reorganized Society soon established its stability and relevance as a social, intellectual and political group; papers were presented at every meeting and lobbying efforts resulted in the first State Medical Practice law in 1876. There were continuing membership problems, though, and by the turn of the century institutional and regional rivalries (the Southern California Medical Society had been formed in 1888) had led to consideration of a second reorganization. California sent delegates to the American Medical Association's 1901 reorganization meeting in Indiana. As a result of this meeting the AMA restructured, and the national organization of state units --including the California Medical Association --came into being.