CHI St. Alexius Health Williston Medical Center is a health care facility in Williston, North Dakota. CHI St. Alexius Health Williston is a 25-bed critical access hospital located in Williston, North Dakota. It was founded in 1920 by the Sisters of Mercy to provide quality health care to the growing population of the region. Today, we provide a full range of clinic and hospital services including: Primary Care, Women’s Health, Pediatrics, Orthopedics, Urology, Plastic Surgery, General Surgery and ENT.