structural:expansion
Development

After the failure of the Kinemacolor project, in which Dixon was willing to invest his own money, he began visiting other studios to see if they were interested. In late 1913, Dixon met the film producer Harry Aitken, who was interested in making a film out of The Clansman. Through Aitken, Dixon met Griffith. Like Dixon, Griffith was a Southerner, a fact that Dixon points out; Griffith's father served as a colonel in the Confederate States Army and, like Dixon, viewed Reconstruction negatively. Griffith believed that a passage from The Clansman where Klansmen ride "to the rescue of persecuted white Southerners" could be adapted into a great cinematic sequence. Griffith first announced his intent to adapt Dixon's play to Gish and Walthall after filming Home, Sweet Home in 1914.

Birth of a Nation "follows The Clansman nearly scene by scene." While some sources also credit The Leopard's Spots as source material, Russell Merritt attributes this to "the original 1915 playbills and program for Birth which, eager to flaunt the film's literary pedigree, cited both The Clansman and The Leopard's Spots as sources." According to Karen Crowe, "here is not a single event, word, character, or circumstance taken from The Leopard's Spots.... Any likenesses between the film and The Leopard's Spots occur because some similar scenes, circumstances, and characters appear in both books."

Griffith agreed to pay Thomas Dixon $10,000 (equivalent to $ 304,186 in 2023) for the rights to his play The Clansman. Since he ran out of money and could afford only $2,500 of the original option, Griffith offered Dixon 25 percent interest in the picture. Dixon reluctantly agreed, and the unprecedented success of the film made him rich. Dixon's proceeds were the largest sum any author had received for a motion picture story and amounted to several million dollars. The American historian John Hope Franklin suggested that many aspects of the script for The Birth of a Nation appeared to reflect Dixon's concerns more than Griffith's, as Dixon had an obsession in his novels of describing in loving detail the lynchings of black men which did not reflect Griffith's interests.