Complex sentence: Pathmark is a supermarket chain headquartered in Montvale, New Jersey, founded in 1968 when its parent, Supermarkets General Corporation (now known by the store name), pulled out of the ShopRite retailers' cooperative.
Split into simpler sentences: Pathmark is a supermarket chain headquartered in Montvale, New Jersey. It was founded in 1968 when its parent, Supermarkets General Corporation (now known by the store name), pulled out of the ShopRite retailers' cooperative.