Adolph Marx was born November 23, 1888 in New York City; years later he would change his name to Arthur, because he preferred it to the very German Adolph.

When he was younger, a critic for a Champaign, Illinois paper wrote, "The Marx Brother who plays 'Patsy Brannigan' [Arthur] is made up and costumed to a fare-thee-well and he takes off on an Irish immigrant most amusingly in pantomime. Unfortunately the effect is spoiled when he speaks" (Harpo Speaks; Harpo Marx and Rowland Barber; Chapter 8, "The Silencing of Patsy Brannigan"). Because of this review, Arthur made up his mind to, "...never [utter] another word, onstage or in front of a camera, as a Marx Brother."

On September 28, 1936, Harpo married actress Susan Fleming and together they adopted four children: Bill, Alexander, James Arthur, and Minnie.

Sadly, Harpo died at 8:39 p.m. on September 28, 1964, after heart bypass surgery.