From Wikipedia, the free encyclopedia Jack Leonard "J. L." Warner (August 2, 1892 – September 9, 1978), born Jacob Warner in London, Ontario, was a Canadian-American film executive who was the president and driving force behind the Warner Bros. Studios in Burbank, California. Warner's career spanned some 45 years, its duration surpassing that of any other of the seminal Hollywood studio moguls. As co-head of production at Warner Bros. Studios, he worked with his brother, Sam Warner, to procure...