The 1984 season saw two stand-up roller coasters open in the United States. One was, like Extremeroller, yet another retrofit. The River King Mine Train was an Arrow-built roller coaster that opened with its park, Six Flags St. Louis, in 1971. Stand-up trains were added for 1984, and the attraction's name was changed to Rail Blazer. However, like Extremeroller the season before, the track wasn't intended to use stand-up trains and, prior to the start of the 1985 season, the original trains and name were restored. Also in 1984, 350 miles east of Six Flags St. Louis, Kings Island at Mason, Ohio opened the TOGO-designed King Cobra as the world's first purpose-built stand-up roller coaster. The attraction operated from 1984 to 2001.