The name of the school was changed to Tennessee Military Institute in 1909. It was known by this name for most of its life. Due to the "TMI" acronym, it was often jokingly referred to as "Ten Million Idiots" by locals and students alike. 1909 was also when the school moved to its final campus, which eventually consisted of thirteen buildings mostly contained in a single quadrangle surrounding a courtyard, and which was located on 144 acres (58 ha) on
U.S. Route 11. U.S. Army officers began directing military instruction in 1911.
ROTC began in 1918 after
World War I, as Hulvey's tenure as president ended. Col. C.R. Endsley was TMI's longest serving president, from 1918 to 1956. He was succeeded by his son and namesake, Col. C.R. Endsley Jr. Endsley Jr. was one of the school's longest-serving administrators, serving as commandant from 1934 to 1956, as president from 1956 to 1971, and as head of the chemistry and physics department from 1971 to 1981. Thomas C. Dula succeeded Endsley Jr. as president, serving until the school went
coed in 1973, when Sanford Gray became president, a role he filled until the school's closing. Col. C.W. Price was another of the school's longest-serving administrators, serving as vice-president from 1920 to 1966. David N. McQuiddy was another, who served TMI from 1937 to 1981 as Latin and English headmaster, admissions director, director of testing, and special advisor to the guidance department. TMI's sports teams were called the Eagles, and their colors were orange and blue. == TMI Academy ==