Six Flags Magic Mountain opened in Valencia, California, on May 29, 1971, as a major amusement park in what was then a relatively remote part of Los Angeles County. Developed by the Newhall Land and Farming Company and Sea World Inc., it quickly built an identity through themed characters, live entertainment, and innovative rides. Important milestones included the 1976 debut of Great American Revolution, recognized as the first modern steel looping coaster, and the 1978 opening of Colossus. After Six Flags acquired the park in 1979, it expanded into a leading coaster destination, eventually becoming the first amusement park with 20 roller coasters in 2022.