For many years, dating back to when it first affiliated with the University of California in 1873, the UCSF School of Medicine was the only public medical school in California. This made sense in the late 19th century when most of California's population lived in Northern California and Southern California was a lightly populated desert. It no longer made sense by the 1940s, after Los Angeles had overtaken San Francisco to become the leading metropolis on the West Coast of the United States.