In January of 1910, Harpo joined two of his brothers to form The Three Nightingales. When the Marx Brothers were playing in vaudeville, Harpo was inspired to develop his "silent" routine after reading a review of one largely adlibed performance. The theater critic wrote, "Adolph Marx performed beautiful pantomime which was ruined whenever he spoke".
Harpo changed his name to Arthur during World War I because he thought Adolph was "too German".
Harpo married actress Susan Fleming on September 28, 1936. The couple adopted four children (Bill, Alex, Jimmy and Minnie).
In 1955, Harpo made a memorable appearance on Lucille Ball's popular sitcom, I Love Lucy.
In 1961, Harpo published his autobiography, Harpo speaks.
On September 28, 1964, Harpo died after open heart surgery.