Bottlenecks.

In the late summer of 1787 George Washington made the mistake of trying to cross the stream at Elkton, Maryland, on what he described as "an old rotten, and long disused" bridge. One of his carriage horses fell through, and only the prompt assistance of some bystanders saved the first citizen of the republic from plummeting into the water. Experiences such as Washington's were not uncommon in the early national era. "Roads" were often no more than mud tracks, and few streams could boast permanent all-weather bridge crossings. Most travelers relied on ferries and fords, both subject to the vagaries of the weather, even to cross major rivers. The lack of reliable bridges and roads represented more than just an occasional danger or inconvenience to travelers. During the War of 1812 the nation's armies found the unreliable road-and-bridge system a serious impediment to the timely movement...