Skateboarding originated in California in the late 1940s when surfers wanted something to do on flat days. It grew in popularity in the 1970s with the development of polyurethane wheels and trucks designed for skateboards, allowing for more maneuverability. A key development was the invention of the ollie in 1976 by Alan Gelfand, which allowed skaters to do tricks in mid-air and transformed skateboarding with the adaptation of tricks to flat ground, led by skater Rodney Mullen.