Skateboarding started over 50 years ago when bored surfers had no waves to ride; in order to practice their tricks they put together planks of wood with old roller skate wheels. This was known as sidewalk surfing. Sidewalk surfers found out that they could ride smoother if they used baked clay (commonly called urethane) for the wheels instead of the rattling steel wheels.
By the 1970s all sidewalk surfers were using urethane for wheels. Sidewalk surfing morphed into skateboarding when many sidewalk surfers were searching for tricks to do on their boards, therefore manufactures started to make their boards curved and upturned. This enabled skateboarders (this is what they were now known as) to invent new modern tricks.
One of the most innovative skaters around was Rodney Mullen; he invented nearly every trick we see today including the fundamental tricks as well. Without Rodney Mullen, skateboarding would’ve just died out and would never have become the great pastime that it is today.