Standard Oil was an American oil company founded by John D. Rockefeller in 1870. It quickly grew to dominate the oil industry, controlling about 90% of the U.S. refineries and pipelines at its peak. The company was known for its aggressive business practices, including undercutting competitors and forming trusts to eliminate competition. In 1911, the U.S. Supreme Court ruled that Standard Oil was violating antitrust laws and ordered its breakup into 34 smaller companies. This landmark decision helped shape modern corporate regulations and led to the creation of several well-known companies, including ExxonMobil and Chevron.