New Mexico Military Institute was founded by Colonel Robert S. Goss and Captain Joseph C. Lea in 1891, originally as the Goss Military Institute, with an initial enrollment of 38 students. Captain Joseph C. Lea, originally from Tennessee, served in the Civil War before relocating to Chaves County New Mexico in 1878. The 1902 Bronco yearbook was inscribed with the dedication "To Captain Joseph C. Lea, the father of the Institute who originated the idea of a military school in Roswell, and who throughout its existence has been the best friend of the school and its cadets." Goss Military Institute was recognized by the territorial legislature and renamed New Mexico Military Institute (NMMI) in 1893. While the legislature had recognized the school, it failed to provide funding, and the school was forced to close its doors on "Bad Friday", March 29, 1895. In the winter of 1894–1895 a funding bill was prepared and approved by the legislature.
James J. Hagerman donated a tract of land which became the current location of the institute. The school reopened in the fall of 1898. In 1909 NMMI received its first classification as a Distinguished Military Institution. In 1917 NMMI received its first accreditation by the North Central Association of college and Secondary Schools. In 1919 the Spanish influenza pandemic reached NMMI and affected nearly two thirds of the cadets resulting in 3 deaths. Classes continued during the 6 week long quarantine. and hotelier
Conrad Hilton of the
Hilton Hotels chain. In 1948, the institute introduced a four-year liberal arts college program but discontinued it in 1956. The school became fully coeducational in 1977, although some females had attended as non-cadet day students from 1891 to 1898. In 1991 NMMI held a yearlong celebration of its centennial anniversary. NMMI horses were auctioned off in 1997 due to the rising costs of insuring the equestrian programs and caring for the horses, this ended all equestrian programs on campus. Members of the alumni association claimed that this was an effort by the school to gain access and control of the over $5.2 million in assets of the association. On June 10, 2013, the school filed a lawsuit in
Chaves County to take control of the assets of the alumni association. Editorial response to the institute's actions has been generally negative, calling it a "hijacking" of the group and its resources. On April 21, 2015, the Fifth Judicial District Court found that the alumni association had not breached its agreement with NMMI and that NMMI had "improperly terminated" the agreement. The judge required the association to turn over the funds. In 2020 NMMI once again saw a pandemic, COVID-19, which resulted in cadets being sent home on spring break in March and not returning to campus until the start of the fall semester in August under strict health protocols. ==Campus==