The son of actors, William Farnum was 12 years old when he joined his parents and his brother Dustin and Marshal in the family business. Dustin (1874-1929) made it to motion-picture stardom first, as leading man of Cecil B. DeMille's first feature, 1914's The Squaw Man. That same year, William made his movie debut in another popular western, The Spoilers (1914). The climactic fight scene between Farnum and co-star Tom Santschi made stars out of both men, though only Farnum graduated to matinee-idol status.
Signing with Fox films in 1915, Farnum became one of that studio's most popular leading men, thanks to such solid vehicles as Tale of Two Cities (1917), Les Miserables (1917) and If I Were King (1920). At his peak, Farnum was pulling down $10,000 dollars per week.
He briefly returned to Broadway in 1925 to star in The Buccaneer. Later in 1925, Farnum suffered a serious injury on the set of The Man Who Fights Alone; as a result, he was confined to supporting roles for the rest of career. While many of these roles were sizeable (notably King Arthur in the 1931 Will Rogers version of A Connecticut Yankee), Farnum would never again recapture the glory of his silent stardom.
William Farnum remained a busy character actor up until his death in 1952, often playing minor roles in remakes of his silent triumphs--including the 1942 remake of The Spoilers.