The American Military Frontiers

As the fledgling nation looked west to the land beyond the Appalachian Mountains, it turned to the army to advance and defend its national interests. Clashing with Spain, Britain, France, Mexico, the Confederacy, and Indians in this pursuit of expansion, the army's failures and successes alternately delayed and hastened western migration. Roads, river improvements, and railroads, often constructed or facilitated by the army, further solidified the nation's presence as it reached the Pacific Ocea