Holly Energy Partners LP operates a network of refined products and crude oil pipelines, with attendant terminal assets, in several western and southwestern states. Independent oil refiner Holly Corporation, now HollyFrontier, formed HEP in 2004 to acquire and operate pipelines and storage assets. HEP's core pipelines are linked to HollyFrontier's own refineries and Alon's Big Spring refinery in Texas. The partnership owns most of the mileage it operates.