This paper examines the work of two novelists from the turn of the twentieth century, one black and one white, whose sharply contrasting, almost mirror-image fictions experimented with redefining citizenship along racial lines. Both Sutton Griggs and Thomas Dixon saw the U.S. as suffering from a constitutional vacuum, an absence of legitimate authority that had left one racial group at the mercy of another. Both imagined the victimised group drawing its ‘citizens’ together in a secretive underground designed to supply the missing constitutional forms: for Griggs, the Imperium in Imperio, a fictional shadow government of and for African-Americans, and for Dixon the Ku Klux Klan, cast as heroes in the tales that later became the landmark film The Birth of a Nation. Necessarily operating from hidden sites – secluded woods, caves, a whole concealed ‘capital’ – Griggs’ and Dixon’s clandestine quasi-governments finally self-destruct, and the similar failures of these two very different ‘nations within the nation’ point, in turn, to contradictions inherent in trying to make citizenship a function of race.