The transformation by which the slender line of the Indian trail became the trader's trace, and then a road, superseded by the turnpike and canal, and again replaced by the railroad, is typical of the economic development of the United States. As the population of the west increased, its surplus products sought outlets. Improved means of communication became essential, and when these were furnished the new lines of internal trade knitted the nation into organic unity and replaced the former colonial dependence upon Europe, in the matter of commerce, by an extensive domestic trade between the various sections. From these changes flowed important political results. [Footnote: For the earlier phase of internal improvements, cf. Babcock, Am. Nationality (Am. Nation, XIII.), chap. xv.]

Many natural obstacles checked this process. The Appalachian mountain system cut off the seaboard of the United States from the interior. From the beginning, the Alleghenies profoundly influenced the course of American history, and at one time even endangered the permanency of the Union. In our own day the railroad has so reduced the importance of these mountains that it is difficult for us to realize the part which they once played in our development. Although Webster boasted that there were no Alleghenies in his politics, we have already seen [Footnote: See chaps, iii., vi., above.] that in the twenties they exercised a dominant influence on the lines of internal commerce, and compelled the pioneer farmers to ship their surplus down the Mississippi to New Orleans and around the coast, and thence abroad and to the cities of the north. The difficult and expensive process of wagoning goods from Philadelphia and Baltimore across the mountains to the Ohio Valley raised the price of manufactured goods to the western farmer; while, on the other hand, the cost of transportation for his crops left him little profit and reduced the value of his lands. [Footnote: Journ. of Polit. Econ., VIII., 36-41.]

Under these circumstances, it was inevitable that the natural opportunities furnished by the water system of the Great Lakes and the widely ramifying tributaries of the Mississippi should appeal to statesmen who considered the short distances that intervened between these navigable waters and the rivers that sought the Atlantic. Turnpikes and canals had already shown themselves practicable and profitable in England, so a natural effort arose to use them in aid of that movement for connecting east and west by ties of interest which Washington had so much at heart. New York, Pennsylvania, Maryland, and Virginia, all subdivided by the mountains into eastern and western sections, fostered roads and chartered turnpike and canal companies. Pennsylvania was pre-eminent in this movement even before the close of the eighteenth century, subscribing large amounts to the stock of turnpike companies in order to promote the trade between Philadelphia and the growing population in the region of Pittsburgh. So numerous were the projects and beginnings of roads and canals in the nation, that as early as 1808 the far-sighted Gallatin made his famous report for a complete national system of roads and canals. [Footnote: Cf. Hart, Slavery and Abolition (Am. Nation, XVI.), chap. iii.]

When New York undertook the Erie Canal in 1817 as a state enterprise, and pushed it to such a triumphant conclusion that before a decade after its completion its tolls repaid the cost of construction, a revolution was effected in transportation. The cheapness of water carriage not only compelled the freighters on the turnpike roads to lower their charges, but also soon made it probable that canals would supersede land transportation for heavy freights, and even for passengers. For a time the power of Pittsburgh and the activity of Philadelphia merchants sustained the importance of the Pennsylvania turnpike. Until Great Lake steam navigation developed and population spread along the shore of Lake Erie and canals joined the Ohio and the lakes, the Erie Canal did not reap its harvest of trade in the west. But already Pennsylvania was alarmed at the prospect of losing her commercial ascendancy. While New York and Philadelphia were developing canals and turnpikes to reach the west, Baltimore was placed in an awkward position. The attempts to improve the waters of the upper Potomac engaged the interests of Maryland and Virginia from the days of Washington. But the success of the Potomac Company, chartered jointly by these two states in an effort to reach the Ohio trade, would have turned traffic towards the city of Washington and its outlying suburbs instead of towards Baltimore, which was already connected by a turnpike with the Cumberland Road, so as to share with Philadelphia in the wagon trade to the Ohio. On the other hand, Baltimore was interested in the development of the Susquehanna's navigation, for this river had its outlet in Chesapeake Bay, near enough to Baltimore to make that city its entrepot; and it tapped the great valley of Pennsylvania as well as the growing agricultural area of south-central New York, which was not tributary to the Erie Canal. But it was not possible to expect New York, Pennsylvania, or even that part of Maryland interested in the Potomac to aid these ambitions of Baltimore; and that city found itself at a disadvantage and Maryland's interests were divided. [Footnote: Hulbert, Historic Highways, XIII., 69 et seq.; Mills, Treatise on Inland Navig.; see chap, xvii., below.]