The records in this section include correspondence and papers about MacMurray's career in the regular army, which he entered in February 1866, including service records and correspondence about commissions, promotions, and detail as professor of Military Science and Tactics at the University of Missouri (1872-1873) and at Cornell (1873-1875). There is little documentation, however, about his detached service at Union College, Schenectady, NY (1879-1883).

The papers include some correspondence and notifications MacMurray received during his service in camps on Buck Creek, Texas and Indian territory (1876), and an undated report or testimonial from sergeant William Boyd about desertions in the army when MacMurray was in charge of Battery "L" 1st Artillery (circa 1883). Of particular interest are MacMurray's papers for June-August 1884, when he served as Special Inspector of Indian Affairs at the Military Department of the Columbia at Vancouver Barracks. Preceded by copies of military correspondence and reports from March 1883, the papers include reports received as well as draft reports by MacMurray himself (July-October, 1884). A notebook that MacMurray kept during this period may be found in Series 5 (Box 85, folder 6). MacMurray recounted his observations about the American Indians in this area and his meetings with their leader and prophet Smohalla in his lecture 'The 'Dreamers' of the Columbia River Valley in Washington Territory' at the Albany Institute in 1886. Additional views about Smohalla's teachings can be found in letters that MacMurray wrote to General Miles in November 1890 (Box 2, folder 3).

The correspondence and papers for 1892-1893 mainly consist of recommendations for a promotion, and do not contain records concerning his service in Sandy Hook, New Jersey, during the cholera scare. The records for 1896-1898, when MacMurray was in command of the Post of Fort Barrancas, Florida, include his reports about the outbreak of yellow fever in 1897.