CHPSO was established by the California Hospital Association (CHA) in 2009. The longest-listed patient safety organization (PSO) in the United States, CHPSO is also one of the largest — it began in California, and over the years added members in Arizona, Hawaii, New Mexico, Nevada, Oregon, Texas, and Washington. In the last quarter of 2019 and into early 2020, CHPSO will see a major expansion to a total of 19 states and nearly 550 members. The vast majority of CHPSO facilities are acute care facilities, but CHPSO members also include ambulatory clinics, home health agencies, hospice care providers, and specialty hospitals.