SEIU Local 250 organized in San Francisco in 1934, when a group of workers at San Francisco General Hospital joined forces to fight for better wages and working conditions. The union was chartered by the American Federation of Labor (AFL) as a federal union on September 13, 1934. It affiliated with the Building Service Employees International Union in 1938 (which became known as the Service Employees International Union in 1968). During the following decades, Local 250 won agreements with major hospitals in San Francisco and in the East Bay, including the 11-member San Francisco Hospital Conference, the Associated Hospitals of the East Bay, and Kaiser Permanente. Organizers secured job classifications and wage increases, the first comprehensive employer-paid health and welfare plan for hospital workers, the first retirement plan, and the first detailed seniority system. By the end of the 1970s, Local 250 membership had reached almost 15,000 and the union represented nursing home workers as well as hospital employees.

In 1987, after a seven-week strike and costly negotiation with Kaiser management over a new “two-tier” wage plan, Local 250 came under the trusteeship of the SEIU. The International Union implemented a new industry-based division structure and updated the organization’s Constitution and By-laws. Local 250 continued to organize healthcare workers and reached out to paramedics, Emergency Medical Services personnel, and convalescent hospital staff. In 1988 the union faced off against the Affiliated Hospitals of San Francisco in a historic strike involving 1,700 members protesting new wage scales and benefits policies. After a successful resolution SEIU returned Local 250 to local control, and the membership elected leaders Sal Rosselli and Shirley Ware in November 1988. Under their leadership Local 250 negotiated a major contract with Kaiser in 1989 and restored a more positive relationship between the hospital and its workers.

During the 1990s and 2000s Local 250 pursued contracts with dozens of facilities in the healthcare system, operated by large corporations including Kaiser Permanente, the Hospital Corporation of America (HCA), Catholic Healthcare West (CHW), Daughters of Charity Health System (DOCHS) and Sutter Health. The union’s membership grew to over 100,000. In 2005, the union merged with the Los Angeles-based SEIU Local 399, to become United Healthcare Workers-West (UHW).