Marion Snow Alexander was born in Kansas City, Missouri, on 23 May 1915, son of Vernon M. and Mary Snow Alexander. He attended Armour Institute of Technology in 1933-34, and in 1937 was graduated with the degree of Bachelor of Science in Mechanical Engineering from Missouri School of Mines. He entered the Naval Service on 30 April 1937 and from July of that year until 11 July 1938 had flight training at the Naval Air Station, Pensacola, Florida. Designated Naval Aviator on 11 July 1938, he was commissioned Ensign on 1 August, that year, and subsequently advanced to the rank of Commander, to date from 5 November 1945.
During the period August 1938 until August 1941, he served as Assistant Gunnery Officer and Navigator of Torpedo Squadron 3 and from January to August 1941 was Gunnery Officer of Scouting Squadron 42, on Neutrality Patrol. He then served for two years as flight instructor at the Naval Air Station, Corpus Christi, Texas, and from September to December 1943 was Executive Officer of Torpedo Squadron 15. During the latter period of World War II he was in command of Composite Squadron 79, operating in the Pacific and Western Pacific war areas.
He was awarded the Air Medal and cited in part, as follows: "For meritorious achievement in aerial flight as Commanding Officer of Composite Squadron 79 attached to the USS SARGENT BAY in action against enemy Japanese forces in active combat zones of the South West and Western Pacific Ocean Areas from December 29, 1944 to January 27, 1945. Leading his squadron on five anti-submarine patrols, combat air patrols and search missions, Lieutenant Commander Alexander rendered valiant service throughout each vital assignment despite the menace of enemy air patrol, active enemy submarine operations and the danger of extremely hazardous weather conditions, and...contributed essentially to the success of his squadron and the fulfillment of these important missions..."
After the cessation of hostilities, from December 1945 until February 1946, he was Navigator of USS Takanis Bay (CVE-89), then reported to the Navy Department, Washington, DC, for a tour of duty in the Office of Naval Intelligence. He was detached in June 1947, and the next year was a student at the General Line School, Newport, Rhode Island. From July 1948 until April 1950 he was Commanding Officer of Fleet Air Service Squadron 9, this assignment followed by duty for more than two years as Executive Officer and Chief Staff Officer to Commander New York Group, Atlantic Reserve Fleet.
From August 1952 until June 1954, he was at sea, first as Executive Officer, later Commanding Officer of USS Palau (CVE-122), which participated in operations against Communist forces in Korea, under the UN Command. He returned to the Navy Department in July 1954, for duty as assistant Head of the Aviation Liaison Branch, and in October 1956 was detached with orders as Executive Officer of the Naval Station, Roosevelt Roads, Puerto Rico.
In addition to the Air Medal, Captain Alexander had the American Defense Service Medal, with star; the American Campaign Medal; Asiatic-Pacific Campaign Medal; World War II Victory Medal; National Defense Service Medal; Korean Service Medal with stars; United Nations Service Medal; and the Philippine Liberation Ribbon with one star.
Captain Alexander was a member of Tau Beta Pi fraternity and Free and Accepted Masons.