Here is the information I found ont he United States Army song. It is also from Wikipedia, but I think it is pretty accurate.
The song is based on the "Caisson Song" written by field artillery First Lieutenant (later Brigadier General) Edmund L. Gruber, Lieutenant William Bryden, and Lieutenant (later Major General) Robert Danford while stationed at Fort Stotsenburg in the Philippines in March 1908.
The tune quickly became popular in field artillery units. In 1917 the Secretary of the Navy and Army Lieutenant George Friedlander of the 306th Field Artillery asked John Philip Sousa to create a march using the "Caisson Song." Sousa changed the key, harmony, and rhythm and renamed it "U.S. Field Artillery."
The recording sold 750,000 copies. Sousa didn't know who had written the song and had been told that it dated back to the Civil War. Although an Army magazine claims that Souza passed on his royalties to Gruber. Other sources state that Gruber became involved in a prolonged legal battle to recover the rights to music he had written and that had been lifted (unknowingly or not) by Souza and widely sold by sheet music publishers who reaped profits while Gruber received nothing.
The music became so popular that it was also used in radio ads by firms such as the Hoover Vacuum Company. Gruber lost his battle in the courts. They ruled that he had waited too long to complain and that his music was by that time in the public domain. "The Caisson Song" was never designated as the official U.S.Army song likely because the lyrics were too closely identified with the field artillery and not the entire army. The official song retains Gruber's music, but with re-written lyrics.
As the Navy, Marine Corps, Air Force, and Coast Guard had already adopted official songs, the Army was anxious to find a song of its own. In 1948, the Army conducted a contest to find an official song, but no entry received much popular support. In 1952, Secretary of the Army Frank Pace asked the music industry to submit songs and received over 800 submissions. "The Army's Always There" by Sam Stept won the contest, and an Army band performed it at President Dwight D. Eisenhower's inaugural parade on January 20, 1953. However, many thought that the tune was too similar to "I've Got a Lovely Bunch of Coconuts," so the Army decided to keep Gruber's melody from the "Caisson Song" but with new lyrics. A submission of lyrics by Harold W. Arberg, a music advisor to the Adjutant General, was accepted. Secretary of the Army Wilber Marion Brucker dedicated the music on Veterans Day, November 11, 1956. The song is played at the conclusion of most U.S. Army ceremonies, and all soldiers are expected to stand at attention and sing. When more than one service song is played, they are played in the order specified by Army regulations: Army, Marine Corps, Navy, Air Force, and Coast Guard.
First to fight for the right,
And to build the Nation’s might,
And The Army Goes Rolling Along
Proud of all we have done,
Fighting till the battle’s won,
And the Army Goes Rolling Along.
Then it's Hi! Hi! Hey!
The Army's on its way.
Count off the cadence loud and strong*
For where e’er we go,
You will always know
That The Army Goes Rolling Along.