The Appalachian Trail (The AT) is one of the longest continuously marked footpath in the world, measuring roughly 2,180 miles in length. The Trail goes through fourteen states along the crests and valleys of the Appalachian mountain range from the southern terminus at Springer Mountain, Georgia, to the Trail’s northern terminus at Katahdin, Maine.
The Delaware & Lehigh Trail connects to the AT near Palmerton, PA. The Schuylkill River Trail connects to the AT in Port Clinton, PA (although both trails have incomplete sections between the AT and Philadelphia). You can learn more information about the Appalachian Trail at http://www.appalachiantrail.org.