This article from The Tennessean details some of the history of chiropractic and subsequent growth of the industry.
September 21, 2012 – In 1895, Harvey Lillard was working as a janitor, maintaining a building in Davenport, Iowa, when he complained about his hearing to one of the tenants, Daniel David “D.D.” Palmer. Palmer had a magnetic healing clinic in the building, and thought that many ailments were the result of misaligned bones and the inflammation they caused that blocked nerve pathways and energy flows in our bodies. He thought that if the alignment were corrected, a patient’s symptoms would alleviate.
Lillard’s story of his hearing loss captured Palmer’s attention. The African-American janitor told Palmer he had lost much of his hearing about 17 years earlier when he “heard something ‘pop’ in his spine,” according to an interview Palmer gave several years later. After several months, he convinced Lillard he could help, and on Sept. 18, 1895, (though the exact day is disputed) manipulated and adjusted the 49-year-old man’s spine.
Palmer used Lillard’s testimony on the quick, and lasting, results from the treatment to encourage others to try his method of manipulation, and he expanded his treatments to include spine manipulations. He opened the Palmer School and Cure in 1897, the first school for teaching chiropractic, a term he coined from Greek words with the help of a patient.
Source: The Tennessean, by Frank Daniels III