He was born in Thibodaux, Louisiana and was the son of Justin de La Garde and Aurelia Daspit, both members of colonial French families.

He left Roosevelt Hospital to accept an appointment as acting assistant surgeon in the Army, effective March 30, 1874, and joined the service at Fort Wallace, Kansas.

While at the latter post he took leave in 1881 and was married in Franklin, Kentucky, to Frances Neely, of a pioneer family, which for generations had furnished physicians to their community.

(1884–86), in the Yellowstone National Park (1886–87), and at Fort Assinniboine to April 1891, at which time he had completed fifteen years of continuous frontier duty.

He came east to Fort McHenry, Maryland, in May 1891 and took up studies on bacteriology and pathology at Johns Hopkins University and assembled the equipment for a clinical laboratory for a general hospital which he was ordered to establish and command at the World’s Columbian Exposition in Chicago in 1893.

He served with this hospital in Jackson Park from February to November 1893, acting also as attending surgeon to all officers and men on duty with the exposition.

On July 20, 1892, he was ordered to conduct experiments in cooperation with officers of the Ordnance Department at Frankford Arsenal, Pa., on the effects of small-arm fire with the new calibers and new velocities upon the human body.

He presented an enlarged paper on this subject before the military section of the first Pan-American Medical Congress which met in Washington in September 1893.

He accompanied the 9th Cavalry to the Pine Ridge Agency in September 1897 and with the onset of the Spanish–American War went with that regiment to Chickamauga Park and thence to Tampa, Florida, in May 1898.

While on this duty he was charged with the evacuation of the wounded to the United States, and, upon the appearance of yellow fever, with the establishment of a special hospital for that disease.

From October 1903 to May 1904 he served as president of a board to study the stopping power of pistols and revolvers, involving tests made in Washington, New York, and Chicago.

Though filling many administrative posts during his long military service, his first interest was the practice of medicine, with a special bent toward surgery and diseases of the eye.

Following his retirement La Garde made his home in Washington and set to work upon his book Gunshot Injuries: How they are Inflicted, their Complications and Treatment, which was published in 1911, with a second edition in 1916.