Abstract: This work examines what constituted 19th century American military science, why it was framed within government policy and taught within the United States Military Academy, and how it became the early American way of war. The work uses as evidence a wide array of documents including biographical records of 2046 West Point graduates. It tracks the evolution of military science from Enlightenment Europe to the United States during the American Revolution and its relative obscurity until after the War of 1812. It then explains why a deliberate decision was made to transplant a French Napoleonic version of military science to serve as the curriculum of the military academy and to support the formulation of a national defense policy that called for militarized coastal frontiers and an “expansible army.” The work then follows how and why military science was modified during the period 1820-1860 in response to changes to the threats to the United States, changes related to state and federal plans for “internal improvements,” Indian wars, westward expansion, war with Mexico, and advances in military technology. Specifically it tracks how the doctrine of military science evolved from the teaching of specific Napoleonic applications to embrace subjects needed for war in North America. Inculcation in this American military science eventually came to provide the army with an officer corps that shared a common all-arms doctrine and common skill in using mathematics for military problem-solving. The majority of long-service graduates went on to spend years of their career fulfilling general staff, engineering, or academy instructor functions. The proliferation of military science through their work, and through published texts available to state volunteers, ensured that on the eve of the Civil War there existed a distinctly American, and scientific, way of war. This work challenges two late 20th century liberal arts revisionist schools, championed by Samuel Huntington and Russell Weigley, that have unfairly reduced military science to near oblivion.