excerpt from Wikipedia

[The history of chiropractic began in 1895 when Daniel David Palmer of Iowa performed the first chiropractic adjustment on a partially deaf janitor, Harvey Lillard. While Lillard was working without his shirt on in Palmers office, Lillard bent over to empty the trash can Palmer noticed that Lillard had a vertebra out of position. Palmer then asked Lillard what happened and Lillard replied, "I moved the wrong way and I heard a 'pop' in my back and that's when I lost my hearing." Palmer who was also involved in many other natural healing philosophy's had Lillard lay face down on the floor and Palmer proceeded with the adjustment. The very next day, Lillard told Palmer, "I can hear that rackets on the streets."]

To read more about the interesting history of chiropractic you can see the whole article on Wikipedia at History of Chiropractic.