The University of California, San Francisco (UCSF), is a research university located in San Francisco, California and part of the University of California system. The university is entirely dedicated to health sciences and is a major center of medical and biological research and teaching, and is ranked as one of the top universities in the biomedical field in the country and around the world. It was founded as Toland Medical College in 1864, and in 1873 it became affiliated with the University of California. The UCSF School of Medicine is the oldest medical school in the Western United States. 

The UCSF School of Medicine is one of the most selective medical schools in the United States based on average MCAT score, GPA, and acceptance rate. In 2017, 8,078 people applied and 505 were interviewed for 145 positions in the entering class. UCSF is ranked 3rd among research-oriented medical schools in the United States and ranked 3rd for primary care by "U.S. News and World Report," making it the only medical school to achieve a top-5 ranking in both categories. UCSF is currently ranked 3rd among medical schools in the world by the Academic Ranking of World Universities (Clinical Medicine, 2016). 

The UCSF Medical Center is the nation's 5th-ranked hospital and 1st-ranked hospital in California according to "U.S. News & World Report". In 2014, a national evaluation of residency programs named UCSF and the Johns Hopkins School of Medicine the top two physician training institutions in the United States. With 25,398 employees, UCSF is the second largest employer in San Francisco.
what happened in 1873?
1873 it became affiliated with the University of California.