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 was what supported the road and the traffic upon it and that the function of the road crust was only to protect the basement soil from wetting and abrasion. His roads, 6 to 10 inches thick, were made of angular broken stones, all passing a 2-inch ring and packed by traffic until they interlocked into a dense mass. The first American road built according to McAdam’s principles was the Boonsborough to Hagerstown Turnpike in Maryland, completed in 1822.

Rolling stone with steam roller near Westfleld, Mass. in 1898.

McAdam was primarily an administrator, rather than an engineer. Like Trésaguet, he insisted on thorough and continuous maintenance. He also advocated payment of adequate salaries to attract good men who would make roadbuilding a career.

As might be expected, the administration of turnpikes varied widely from company to company, depending on the quality of the management, the amount of toll-paying traffic, and how well the roads were originally laid out and constructed. Many were underfinanced, and failures and reorganizations were frequent. The standard of maintenance was not always as high as it should have been, especially for those roads that were not making much money. But on the whole, the turnpikes were a vast improvement over both the miserable roads and tracks that preceded them and the equally bad local roads still under township control.

In 1808 Benjamin Latrobe, the distinguished architect and civil engineer, and one of the designers of the U.S. Capitol, summarized the prospects of railroads as a national mode of transportation in these words: . . . railroads are out of the question as to the carriage of common articles. Railroads leading from the coal mines to the margin of the James River, might answer their expense, or others from the marble quarries near Philadelphia to the Schuylkill. But these are the only instances, within my knowledge, in which they at present might be employed. There is, however, a use for railroads as a temporary means to overcome the most difficult parts of artificial navigation ; and for this they are invaluable. . ..

Latrobe’s objection to railroads concerned the specialized iron-wheeled carriages required to travel on them; these were too expensive for the average farmer or shipper to own, and also unsuitable for operation on the common roads. Because of this restriction, only specialized roads hauling large quantities of bulk freight, such as coal, from a single source would be able to collect sufficient tolls from traffic to pay out their construction cost. 13