arpo was born Adolph Marx on November 23, 1888. He joined the family act because his mother was looking to add to it just when Harpo had become unemployed. Harpo began to develop the pantomime for which he eventually became so well known, but his roles in their sketches involved speaking, until he read one review. The review complimented Harpo's excellent and hilarious pantomime style, but claimed the effect was completely spoiled when he spoke. Harpo realized he couldn't outtalk Groucho or Chico, and shouldn't even try. He never spoke another word on stage or in front of a camera, as a Marx Brother. Harpo's nickname came from the harp that he had worked into his act, and that he played in nearly every film.

In 1949, Harpo wanted to make a solo film, like Groucho had with Copacabana. He devised the film Love Happy as a starring vehicle for himself, but when Chico was short on money and looking to take part, Harpo brought his brother in. Then the studio insisted that Groucho be included so they could sell it as a Marx Brothers movie. The film did poorly, because it was neither a full-fledged Marx Brothers film, nor a good picture by any standard. It is most notable because it includes Marilyn Monroe in an early bit part. Harpo did occasional television appearances throughout the 1950s. He died following heart surgery on September 28, 1964.