From the beginning, American cinema has been both a powerful mythmaker and a social critic. D.W. Griffith's Birth of a Nation, arguably the first feature film, shows us just how early in its history cinema had established its influence. In 1915 it was the first movie to be screened at the White House. After the screening, President Woodrow Wilson is rumored to have said, "It's like history writ with lightning. And my only regret is that it is all...