Napoleon Bonaparte may not have succeeded in conquering the nations of Europe, but he did conquer the nineteenth century. All major, and most minor, European thinkers wrote about Napoleon, some celebrating his accomplishments, others deploring his example. His success was not limited to Europe, however; Americans were as fascinated by Bonaparte as their European counterparts. The circulation of Napoleon across the century - the ceaseless repetition of his life, achievements, failings, and example - thus created an alternative Napoleonic empire, distinct from its political antecedent and more formative for the century's culture. This article focuses on one episode in that empire's history: the midcentury attempts to account for the social role of greatness or genius. Napoleon is both the chief subject of these efforts and their primary cause, a historical actor who becomes a philosophical problem. After sketching the cosmopolitan contours of the lively midcentury debate about genius, the article examines two American representations of Napoleon: John Abbott's Napoleon Bonaparte, serialized in Harper's Monthly (1851-1855), and Ralph Waldo Emerson's "Napoleon, or the Man of the World" from Representative Men: Seven Lectures (1850) to explain how the French emperor's conquest shaped US thought in the 1850s. © 2015 The Author. Published by Oxford University Press. All rights reserved.