On Monday, U.S. Health Secretary Robert F. Kennedy Jr. is calling for an end to fluoridation in American communities, but when – and why – did the practice start? Grand Rapids, Michigan became the first city in the world to add fluoride to drinking water in 1945 as part of a study first sponsored by the U.S. Surgeon General, then taken over by the National Institute of Dental and Craniofacial Research (NIDR). The 15-year study of nearly 30,000 schoolchildren found that the cavities rate dropped more than 60 percent, according to the NIDR.