American historians have traditionally divided the late nineteenth and early twentieth centuries into Reconstruction, the Gilded Age, and the Progressive Era; however, this arbitrary periodization obscures more than it reveals. My dissertation argues that the Republican and Democratic Parties—like the American nation—passed through a period of reconstruction. Using the four-way presidential elections of 1860 and 1912 as bookends, I examine national politics through the lens of the two generations of politicians—the Civil War and Progressive generations—who oversaw the United States’ transition from an agricultural to an industrial political economy. The Civil War generation’s inability to address the excesses of industrialization called into question classical liberalism’s emphasis on unfettered individualism for competing visions of a regulatory state. Touching off an internecine intergenerational struggle that spread from Democrats, in 1896, to Republicans, in 1912, both parties coalesced around competing visions of a federal regulatory state that took shape, ultimately establishing the ideological foundation of modern