Filmed in Philadelphia by the Lubin Company, The Unwritten Law was a re-creation of the sensational 1906 murder of architect Stanford White by millionaire Harry K. Thaw. Those familiar with such films as The Girl in the Red Velvet Swing and Ragtime will recall that Thaw killed White on the Winter Garden Roof in New York City in full view of hundreds of patrons. Convinced that White had stolen his wife, former "Gibson Girl" Evelyn Nesbitt, Thaw was certain that he would be acquitted on the basis of the "unwritten law." As it turned out, he was sent to a mental institution, rescued from the hangman's noose by his mother's millions. The outcome of Thaw's trial was still up in the air when The Unwritten Law was completed in early 1907, so the film speculated on the future by showing the defendant being acquitted!