<Tr> <Th> Roller coasters </Th> <Td> 9 </Td> </Tr> <Tr> <Th> Water rides </Th> <Td> </Td> </Tr> <P> Six Flags AstroWorld was a seasonally operated theme park located on approximately 57 acres (23 ha) of land (later expanded to over 75 acres (30 ha)) between Kirby Drive and Fannin Avenue, directly south of Loop 610 in Houston, Texas . Opening on June 1, 1968, it was originally developed and constructed as part of the Astrodomain, the brainchild of local philanthropist and former Houston mayor Judge Roy Hofheinz, who intended it to complement The Astrodome . </P> <P> AstroWorld was sold to the Six Flags Corporation by the Hofheinz family in 1975 . Although the fourth park to be included in the Six Flags family of theme parks, it was the first park to be purchased by that company instead of being built . It was marketed as "AstroWorld: A Member of the Six Flags Family" so as to not confuse patrons with Six Flags Over Texas located in Arlington . Many variations of this naming scheme emerged from the Six Flags marketing department over the years . Despite these attempts at branding the park, most people continued to call it "AstroWorld" and the company eventually responded by making the individual park's name more prominent . Similarly, Fiesta Texas in San Antonio has been marketed as "Fiesta Texas: A Six Flags Theme Park". </P>

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