Continental Resources, Inc. is a petroleum and natural gas exploration and production company headquartered in Oklahoma City. The company was founded by Harold Hamm in 1967 at the age of 21 as Shelly Dean Oil Company, originally named for Hamm's two daughters. In 1990, Shelly Dean re-branded itself as Continental Resources. It primarily used hydraulic fracturing and directional drilling to produce from low permeability formations. It is ranked 818th on the Fortune 500.