ExxonMobil Corporation is an American multinational oil and gas corporation headquartered in Spring, Texas, a suburb of Houston. Founded as the largest direct successor of John D. Rockefeller's Standard Oil, the modern company was formed in 1999 following the merger of Exxon and Mobil. It is vertically integrated across the entire oil and gas industry, and within it is also a chemicals division which produces plastic, synthetic rubber, and other chemical products. As the largest U.S.-based oil and gas company, ExxonMobil is the seventh-largest by revenue in the U.S. and 13th-largest in the world. It is the largest investor-owned oil company in the world. Approximately 55.56% of the company's shares are held by institutions, the largest of which as of 2019 were The Vanguard Group (8.15%), BlackRock (6.61%), and State Street Corporation (4.83%).