In June 2012, Wheeling, West Virginia-based Tri-State Petroleum signed a contract to switch 50 stations in Ohio, Pennsylvania, and West Virginia to the Marathon brand. Most of Tri-State's stations before the deal were ExxonMobil-branded stations, the majority Exxon as well as a few scattered Mobil stations in the immediate Wheeling area. Included in the deal were 18 Exxon stations in the Pittsburgh metropolitan area, significantly boosting Marathon's presence in the Pittsburgh market, where former parent company U.S. Steel is based. (Exxon would offset its Pittsburgh losses by taking over the retail contracts of several Shell stations in the area, leaving Shell with a significantly reduced presence, while the Mobil brand was withdrawn from the Northern Panhandle of West Virginia altogether.) Before the deal, Marathon had a much smaller presence in Western Pennsylvania, while having a somewhat larger presence in West Virginia and an almost ubiquitous presence in Southern Ohio.
In 2013, Marathon purchased of numerous assets from BP including a 451,000 barrel per day refinery in Texas City, Texas, four light product distribution terminals, and 1,200 retail stations throughout the southeastern United States.