Planes, trains and automobiles are the types of transport that people use today when migrating from Ireland to the United States. But what about in the 18th century? Obviously, they came to the U.S. by ship, but there was still a considerable distance to cover to reach their final destination.
An excellent article by William Dollarhide, Get On Board the Great Valley Road, outlines the history and geography of colonial wagon trails that linked the ports of the east coast to the then interior of the Carolinas and Virginia. The mostly Scots-Irish immigrants from Ireland would have used these trails to reach their destinations.
Colonial routes of the eastern U.S.
The article further discusses how a knowledge of these routes, and which counties they passed through, is a useful methodological approach for tracing ancestors who traveled them.
It is also a very good example of how the opening of a new route across mountains can influence the port of choice for immigrants. In this article you will see that Philadelphia was the destination of choice. Once the Pioneer Road opened further to the south across the Blue Ridge Mountains, then Alexandria, VA became an important port for the Scots-Irish. You can read the article here.