Alexander Dallas Bache (1806-67) was a key leader of American science in the nineteenth century. Driven by a vision of science as an essential component of an integrated US nation-state, he guided the nascent American Association for the Advancement of Science and led the US Coast Survey, then the nation's largest scientific enterprise. In this analytical biography, Axel Jansen explains and explores Bache's efforts to build and shape public institutions as aids to his goal of creating a national foundation for a shared culture - efforts that culminated during the Civil War when Bache helped found the National Academy of Sciences, which he saw as a key symbol of the continued viability of a unified American nation.