John Oliver McReynolds, physician and teacher, was born on July 23, 1865, in Boonesboro, Kentucky, the son of Richard Bell and Victoria (Campbell) McReynolds. He was a descendent of a number of the leading families of the South—the Boones of Kentucky, the Edwardses of Maryland, and the McReynoldses of Virginia—and traced his ancestry to James McReynolds, who came from Dungannon, Ireland, in 1737. McReynolds received his B.S. from Transylvania University, Lexington, Kentucky, in 1890. Before completing his undergraduate work, he taught mathematics and science at Burritt College in Spencer, Tennessee, in 1886 and mathematics and astronomy at Dallas High School, Dallas, Texas, in 1887–88. He began his medical training at Bellevue Hospital Medical College in New York City and continued his studies at the College of Physicians and Surgeons (later the University of Maryland) in Baltimore. He earned his medical degree in 1891, achieving highest honors in a class of 116. McReynolds served his internship as first assistant resident physician at Baltimore City Hospital, 1891–92, and also studied at eye and ear clinics in New York, Chicago, London, Berlin, Vienna, and Paris. He returned to Dallas in 1892 and joined the practice of Dr. Robert H. Chilton. On November 27, 1895, McReynolds married Katherine Seay, daughter of Judge and Mrs. George E. Seay of Gallatin, Tennessee. They had a daughter. The McReynolds family attended the Central Christian Church of Dallas.
In 1903 McReynolds established the office of McReynolds and Seay (in association with Dero Seay and, later, F. H. Newton), eye, ear, nose, and throat specialists. McReynolds gained worldwide fame with the development of the McReynolds operation for pterygium, a method for removing a growth known as a pterygium from the eye. As devoted to teaching as he was to the practice of medicine, McReynolds and other doctors organized the Texas College of Physicians and Surgeons in 1903. The school was affiliated with Southwestern University in Georgetown until 1911, when it was allied with Southern Methodist University. It closed in 1915. Throughout these transformations, McReynolds served as professor of ophthalmology and otology, sometimes as dean.
McReynolds received many honors for his achievements, including an honorary doctor of science degree from Transylvania University in 1934. In addition to the surgical procedures he developed, he wrote several monographs, served in such professional organizations as the Texas Medical Association and the American Medical Association, served his country as a physician during World War I, took an active role in establishing the commission form of city government in Dallas, and continued to share his knowledge as a teacher. He was one of the pioneers of the use of motion pictures as a teaching tool, and his work in this area was recognized throughout the United States and Canada. McReynolds, who survived his wife by one year, died in his home in Dallas on July 7, 1942. He was survived by his daughter, his son-in-law Frank W. Wozencraft, two grandsons, a sister, and a brother.