After numerous jobs ranging from vaudevillian to fur salesman, Cohn became personal secretary to Universal Studios head Carl Laemmle in 1918. Two years later, with brother Jack and friend Joe Brandt, he formed the CBC Film Sales Company, which formally changed its name to Columbia in 1924. When Brandt left the company, Harry became president of West Coast production and in 1932, after his brother's failure to oust him, took effective control of the studio.
With unscrupulous flair, Cohn turned Columbia into one of Hollywood's most profitable studios but his ruthless tactics also caused a great many stars, directors and screenwriters to despise him (he was nicknamed the 'White Fang' by Ben Hecht). A noteworthy biography by Bob Thomas, entitled "King Cohn", was published in 1967.