As of October 2023, Sansum Clinic's approximately 1,450 physicians and staff represent more than 30 medical specialties and subspecialties at 22 patient care locations.

In 2023, Sansum Clinic joined the Sacramento-based Sutter Health, to bring the benefits of that larger integrated healthcare system to the Central Coast.

In 1920, William D. Sansum (1880–1948) arrived in Santa Barbara, California to serve as head of the Potter Metabolic Clinic.

[6][7] An extensively revised and enlarged version entitled The Normal Diet and Healthful Living, coauthored with Roger Aminiel Hare and Ruth Bowden, was published in 1936.

This was in contrast to the traditional role of clinics at that time which were defined as hospital-based research-oriented facilities, treating patients with specific ailments.

The Cancer Center of Santa Barbara was formed in 1950 with the donation of funds to purchase a one-million-volt x-ray machine.

Though she died, her husband Elisha Converse donated the funds for her doctor, Henry Ullmann, to purchase the x-ray machine in the memory of his wife; it was one of seven in the United States used to treat cancer at the time.

Through the contributions of families and charities, the non-surgical and outpatient center committed itself to advancing the understanding, diagnosis, treatment, cure and prevention of cancer.

Sansum Clinic operates patient care facilities in Carpinteria, Santa Barbara, Goleta and Solvang.

Sansum Clinic was the first place in the United States where insulin was developed and successfully administered to treat diabetes.