[1] In 1846, Murray joined the United States Army as a contracted assistant surgeon, and was posted to Fort Gratiot, Michigan.

[1] Later in 1846, Murray was ordered to duty in California, and after traveling by ship from New York City to San Francisco, he carried out Mexican–American War assignments at military posts in Los Angeles, Monterey, and Sacramento.

[1] In 1852 he was ordered to New York City after his selection as assistant to Major Thomas Gardiner Mower, the Army's Senior Surgeon and Chief Medical Purveyor.

[1] He served at several posts during his second tour of duty there, and worked with other doctors in the state to quell the rampant typhoid fever that accompanied the large population explosion following the U.S. acquisition of California following the war with Mexico.

[2] In the spring of 1861, Murray was ordered to Washington, DC, where he served on the selection board for doctors applying to join the expanding Union Army.

[7] He was responsible for expending and accounting for several million dollars as he acquired medical supplies and equipment for the Union Army, and distributed them to units throughout the country.

[5] He was Medical Director for the Department of the Atlantic from 1880 to 1883, and in 1882 seniority elevated him to the additional duty of Assistant Surgeon General of the United States Army.

[2][8] He was an advocate for creation of the Association of Military Surgeons of the United States, and when the organization formed in 1891, Murray was included as an honorary member.