Highmark is a health insurance company base in Pittsburgh, Pennsylvania, USA. It is the largest health insurer in Pennsylvania, and through a purchase in 1996, the largest health insurer in West Virginia. It primarily serves the western and central parts of Pennsylvania, some areas of eastern Ohio, and all of West Virginia, although it has recently purchased a 40% stake in the largest health insurer in northeastern Pennsylvania as well. It is currently one of the largest not-for-profit health insurers in the United States which owns several for-profit subsidiaries.