Frederick McKay (April 13, 1874 - August 21, 1959) was an American dentist. In 1897 he entered Boston Dental College which later became Dental School of Tufts University. He transferred to the University of Pennsylvania to start his Junior year and graduated in June, 1900. He arrived in Colorado Springs in 1901 and worked as a dental associate for $75.00/ month. He noticed patients with the presence of multiple teeth with white or brown spots and in severe cases the enamel was pitted. He became disturbed that many of his fellow practitioners were apathetic about identifying the cause and solution to this cosmetic problem. McKay spent thirty years investigating the cause of what was then known as the Colorado brown stain, which produced mottled but also cavity-free teeth; with the help of G.V. Black and other researchers, he established that the cause was fluoride. His early observations of mottled enamel and his determination to ascertain its cause led to the discovery of benefits of fluoridation of drinking water. Today, over 300 million people enjoy the benefits of fluoridated water. He died in 1959 at the age of 85.