Born in Danville, Quebec, Canada, Sennett was raised the son of Irish immigrant farmers who moved the family to Connecticut when he was 17. They lived for a time in Northampton, MA where the young Sennett had his first taste of vaudeville as an audience member. After an encounter with fellow Canadian Marie Dressler, the young Sennett was introduced to producer David Belasco and he soon had a new career on the vaudeville stage. In New York, he met the formidable film producer-director D.W. Griffith, for whom he played a bevy of roles at the famed Biograph Company, including the lead in "The Curtain Pole" (1909), Griffith's only attempt at a comedy. He was also noted for portraying sleuth Sherlock Holmes a number of times, but often in more of a comedic representation. Meanwhile, Sennett stumbled into directing by accident when a director fell ill at the last minute and he was told to replace him. Griffith went on to assign him to supervise production of his comedy unit and by 1912, Sennett had set up his own Keystone Studios in Hollywood.Sennett had in effect become America's self-appointed comic showman, and his Keystone operation became a California version of Henry Ford's automobile plant in Michigan. Comedies were cranked out at production-line speed, with several produced in one day from an outline prepared under Sennett's supervision. Drawn directly from the French company Pathe, Sennett instituted a strict formula for his movies despite the appearance of a frenzied freedom onscreen, eschewing characterization in favor of stereotypes for audiences to make an immediate identification. He also issued strict rules governing the type of gags that could be used, with manic car chases and pie tossing becoming comic staples. Meanwhile, the roster of Sennett's talent was impressive, with the likes of Charlie Chaplin, Gloria Swanson, Fatty Arbuckle, Mabel Normand, Harold Lloyd, Raymond Griffith and Frank Capra all working for him. From 1912-17, Keystone became noted for the Sennett Bathing Beauties and the zany antics of the Keystone Kops, a group of anonymous police officers who fumbled their way through a variety of chases while waving their batons to the accompaniment of ragtime piano. Immediately popular, the Keystone Kops were a big hit for Sennett, and even counted unknowns Chaplin and Arbuckle among their ranks early in their careers.But even as early as 1914, Sennett's Kops were relegated to supporting players for Chaplin, Arbuckle and Normand, who began breaking away to become major stars. Meanwhile, he made his first feature-length movie, "Tillie's Punctured Romance" (1914), while continuing to churn out shorts like "In the Clutches of the Gang" (1914) and "Wished on Mabel" (1915). His restrictive methods for making product limited the creative freedom of artists like Chaplin and Arbuckle, who were bursting with ideas and bolted from Keystone at the first opportunity. Even the troubled Mabel Normand, with whom Sennett had a long and rather tumultuous romance, left Keystone in 1918. Still, Sennett refused to change his methods and clung to his threadbare formula, but found enough success to leave Keystone in 1917 to begin independently producing movies, leaving the studio to falter until it finally declared bankruptcy in 1935. Now operating the Mack Sennett Comedies Corporation, Sennett began making more ambitious films with the likes of Billy Bevan, Harry Langdon and cross-eyed comedian Ben Turpin, whose penchant for crude comedy and being of rather unorthodox appearance fit the Sennett mold to a T. While he made many titles throughout the 1920s, most notably "The Extra Girl" (1923) with Normand, Sennett's films were destroyed by distributor Warner Bros. and no longer exist.In the mid-1920s, Sennett chose to begin distributing his pictures through Pathé, which seemed like a shrewd move given the large amount of theaters they distributed to. But when Paramount and MGM began carving away at their market share, Pathé lost a large number of exhibiters and led to hard times for Sennett. By the end of the 1920s, he retooled his operations to accommodate the advent of sound pictures and voided all contracts he had with his players, losing some of his top talent. He did, however, make rather effortless transition and fully embraced the new technology, while even making occasional forays into experimenting with color. But despite his embrace of new technology, Sennett stubbornly clung to outmoded storytelling techniques that felt rather dated in the 1930s, though he did have some success with shorts starring Bing Crosby and W.C. Fields. Meanwhile, he partnered with Paramount Pictures, only to find the relationship last for a year. Unable to pull himself up during the Great Depression, he directed Buster Keaton in one of his last films, "The Timid Young Man" (1935), before lapsing into semi-retirement. He received an honorary Oscar in 1938 and appeared onscreen in several documentaries and compilation films. His Keystone Kops re-emerged in "Abbott and Costello Meet the Keystone Kops" (1955), only to once again slip into obscurity. Five years later, Sennett died on Nov. 5, 1960 in Woodland Hills, CA. He was 80 years old.