[5][6] The family immigrated to the United States when William was nine months old and settled in New York City, where they had twelve more children, of whom only six survived.

To help the family financially [7] William found a job selling candy and newspapers[8] in Central Park.

Between 1915 and 1919, Fox would rake in millions of dollars through films which featured Fox Film's first breakout star Theda Bara, known as "The Vamp", for her performance in A Fool There Was (1915), based on the 1909 Broadway production A Fool There Was by Porter Emerson Browne, in turn based on Rudyard Kipling's poem The Vampire, in turn inspired by Philip Burne-Jones's painting, The Vampire (1897), modelled by Mrs Patrick Campbell, Burne-Jones' lover and George Bernard Shaw's "second famed platonic love affair".

[18] In 1925–1926, Fox purchased the rights to the work of Freeman Harrison Owens, the U.S. rights to the Tri-Ergon system invented by three German inventors (Josef Engl (1893–1942), Hans Vogt (1890–1979), and Joseph Massolle (1889–1957)), and the work of Theodore Case to create the Fox Movietone sound-on-film system, introduced in 1927 with the release of F. W. Murnau's Sunrise: A Song of Two Humans.

Sound-on-film systems such as Movietone and RCA Photophone soon became the standard, and competing sound-on-disc technologies, such as Warner Bros.' Vitaphone, became obsolete.

Mayer used his strong political connections to persuade the Justice Department to sue Fox for violating federal antitrust laws.

By the time he recovered, the stock market crash in October 1929 had wiped out virtually his entire fortune, ending any chance of the Loews-Fox merger going through even if the Justice Department had approved it.

A combination of the stock market crash, Fox's car accident injuries, and government antitrust action, forced him into a protracted seven-year legal battle to stave off bankruptcy.

In 1943, Fox served a five-month and seventeen day prison sentence on charges of conspiring to obstruct justice and defraud the United States, in connection with his bankruptcy.