By the first decade of the 20th century, a number of business entities had formed themselves into trusts, which dominated their industries. Trusts often sought to purchase or otherwise neutralize their competitors, allowing the conglomerates to raise prices to high levels. In 1890, Congress had passed the Sherman Anti-Trust Act, but it was not until the Theodore Roosevelt administration (1901–09) that serious efforts were made to break up or control the trusts. The dominant force in the oil industry was Standard Oil, controlled by John D. Rockefeller. Modern-day ExxonMobil, Atlantic Richfield, Chevron, Sohio, Amoco and Continental Oil all trace their ancestry to various parts of Standard Oil.