In 1816, John C. Calhoun introduced a new proposal for federal aid for road and canal construction. Failure to link the nation together with an adequate system of transportation would, Calhoun warned, lead "to the greatest of calamities--disunion." "Let us," he exclaimed, "bind the republic together with a perfect system of roads and canals. Let us conquer space." Narrowly, Calhoun's proposal passed. But on the day before he left office, Madison vetoed the bill on constitutional grounds