The Birth of a Nation (1915) IMDb
As far as the history of the medium goes, The Birth of a Nation’s significance has been greatly exaggerated by a generation with poor access to older films. At this point the main reason to see it is not for the form but for the ahistorical depiction of the Confederacy, reviving the KKK. It is a coda to the wave of monument-building in the first decade of the 20th century, which sought to legitimize continued racism by celebrating the Confederacy’s betrayal of a nation as a noble “heritage”.
References here: Gone with the Wind (1939).