As the story goes, in 1872 railroad magnate and ex-governor of California Leland Stanford made a bet with a fellow horseman regarding a horse's gallop. Contending that all four of a horse's feet are off the ground simultaneously at some point while galloping, Stanford hired Muybridge to prove it photographically.
Muybridge's first photographs of the horse were poorly exposed and thus inconclusive. After constructing a more efficient shutter and improving the speed of his film, he resumed his experiments with motion studies in 1877, but he was still producing only single images. Undaunted, he developed a system of first twelve and eventually twenty-four cameras, whose electro-magnetic shutter blades were opened by the stride of the animal tripping wires strung across the track. This series of twenty-four consecutive frames, which took less than one second to expose, was made after Muybridge had perfected his technique. Ultimately, Muybridge did prove that all four feet of a galloping horse were off the ground simultaneously.