The development of regional economies helped to complement the growth of nationalism in a way because the regional economies, though separate, were connected. For example, the regional economy of what is now the Midwest was connected by water to the Northeast. Similarly, the Southern economy depended on the North for things like shipping and insurance and some manufactured goods.
Of course, these developments also contradicted each other. The development of regional economies made the regions less similar to one another and less inclined to get along. This contradicted the growing tendency towards more of a national feeling.