July Fourth, "The Star-Spangled Banner," Memorial Day, and the pledge of allegiance are typically thought of as timeless and consensual representations of a national, American culture. In fact, as Cecilia O'Leary shows, most trappings of the nation's icons were modern inventions that were deeply and bitterly contested. While the Civil War determined the survival of the Union, what it meant to be a loyal American remained an open question as the struggle to make a nation moved off of the battlefields and into cultural and political terrain.

Drawing upon a wide variety of original...