Founded by John D. Rockefeller in 1862 in Titusville, PA as Rockefeller & Andrews Oil. Using combination of trust agreement and a holding company based in NJ, grew to totally dominate oil production, transport, and retailing. Standard Oil incorporated 1870.
Trust agreements revoked (court order) 1892; SO holding company broken up 1911 into 35 entities, including: Exxon, Mobil, Chevron, ARCO, Conoco, and Amoco. Amoco and ARCO were absorbed by British Petroleum, while Conoco merged with Phillips, Chevron merged with Texaco, and Exxon merged with Mobil.
Apologies to Urban Dictionary for misspelling the company's name "Exxon Mobile" in the definition for BP, p.l.c..
Exxon Mobil mostly evaded any significant financial responsibility for the 1989 Exxon Valdez tanker crash, the 2nd worst oil spill in US history (since eclipsed by the 2010 Deepwater Horizon blowout. That disaster cost the company about $4.5 billion, paid out over 20 years (or roughly 2% of profits over that time period).