Referred to as both Mark and Marc, he was born in Paducah, Kentucky, the child of Jewish immigrants from Germany.

He formed a partnership with A. L. "Abe" Erlanger that started as a theatrical booking agency in New York City in 1888.

[2] In 1896, Klaw & Erlanger joined with Al Hayman, Charles Frohman, Samuel F. Nixon, and J. Fred Zimmerman to form the "Theatrical Syndicate".

[2][3] Despite being nearly universally despised in the industry for their ruthless tactics, Klaw and Erlanger produced dozens of Broadway plays and financed many others including the early editions of the Ziegfeld Follies.

[citation needed] After his retirement, in 1929 Klaw moved to England, where he died in 1936 at Bracken Fell, Hassocks, West Sussex.