Solomon Harper, an African-American inventor, created the first hair curlers. His model was a thermostatic hair curler, and therefore relied on heat in order to curl hair. He received a patent for his original design in 1930, although he updated his device and applied for a second patent in 1953.
Harper's invention relied on electricity to provide the heat needed to curl hair. The next improvement to hair curlers was developed and patented in 1980 by a hairdresser named Theora Stephens, who developed a pressing/curling iron. Her design was more efficient than Harper's, but similarly relied on heat to curl hair.