which was, therefore, the center of foreign exports for the valley,
as well as the port from which the coastwise trade in the products
of the whole interior departed. In 1830 its population was nearly
fifty thousand.

The rise of an agricultural surplus was transforming the west and
preparing a new influence in the nation. It was this surplus and the
demand for markets that developed the cities just mentioned. As they
grew, the price of land in their neighborhood increased; roads
radiated into the surrounding country; and farmers, whose crops had
been almost worthless from the lack of transportation facilities,
now found it possible to market their surplus at a small profit.
While the west was thus learning the advantages of a home market,
the extension of cotton and sugar cultivation in the south and
southwest gave it a new and valuable market. More and more, the
planters came to rely upon the northwest for their food supplies and
for the mules and horses for their fields. Cotton became the
engrossing interest of the plantation belt, and, while the full
effects of this differentiation of industry did not appear in the
decade of this volume, the beginnings were already visible.
[Footnote: Callender, "Early Transportation and Banking Enterprises
of the States," in Quarterly Journal of Econ., XVII., 3-54.] In
1835, Pitkin [Footnote: Pitkin, Statistical View (1835), 534.]
reckoned the value of the domestic and foreign exports of the
interior as far in excess of the whole exports of the United States
in 1790. Within forty years the development of the interior had
brought about the economic independence of the United States.

During most of the decade the merchandise to supply the interior was
brought laboriously across the mountains by the Pennsylvania