The Sinclair Oil Corporation was founded by Harry F. Sinclair in 1916, notes the Sinclair Oil website. Since then, the Sinclair Oil Corporation has become one of the largest oil companies in the United States.
Sinclair began his career as a druggist, notes the Sinclair Oil website. After his drug store failed, the oil boom was in full swing. He sold lumber for oil derricks, along with buying and selling leases on the side. He purchased leases on land that struck oil. It was then that corporate sponsors became attracted to his business. By 1913, Sinclair was in charge of 62 separate oil companies. Sinclair decided to go out on his own in 1916, just as the Automotive Age began.