This article reconsiders early American state capacity through a close examination of the U.S. Army Corps of Topographical Engineers. The topographical corps, a bureau in the antebellum War Department, developed a form of conditional bureaucratic autonomy far earlier than recognized in previous scholarship, giving it a central role in shaping national economic development policies, especially in the nation's periphery. Unlike robust bureaucratic autonomy, such as that described by Daniel Carpenter (2001, 2010; see footnote 4), conditional autonomy is highly contingent and can quickly fracture if the surrounding environment changes. The long-serving chief of the corps, Col. John J. Abert, shaped the opinions of his supposed principals by managing the ideas, information, and proposals directed to them. When faced with challenges, the corps proved to be a flexible organization that adapted its methods to accomplish its preferred ultimate goals using different instruments. In the end, however, the corps' autonomy was threatened when it became involved in the sectional politics surrounding the potential building of a transcontinental railroad line. Once the corps lost several of the conditions supporting its autonomy, its downfall was swift. This article thus joins a recent wave of scholarship highlighting strengths within the early American state by foregrounding the role of the armed forces in statebuilding.