Amanda,
Have you ever been to the Shenandoah Valley? Augusta has some rivers, all are small and were never navigable. One could take the Great Wagon Road, which later became Valley Pike and is now Route 11. It is paralleled for all practical purposes by Interstate 81. If you take Interstate 81 or Route 11 north from Augusta Cuonty, you follow the Valley north all the way to Harrisburg, PA and never cross any mountains. In the old days if you were going to Philadelphia you headed east out of Winchester and crossed the Potomac at Harper's Ferry, where the Potomac cuts through the Blue Ridge- so you never had to cross "all those mountains." From Harpers Ferry the old road went to Frederick and from there to Gettysburg and then to York. An Augusta County farmer would not have shipped bulk produce to Philadelphia, it was at least a two week trip, and he would have wanted to make it worth while. However, he might distill his apples into brandy and haul a couple of kegs of brandy to Philadelphia. He might grind some wheat into flour and haul some barrels of flour. Or if he had captured some wildlife and had some deerskin and beaver pelts then that would be worth the trip. There were a few Indian raids in the Valley but it never interrupted back and forth travel between Philadelphia and the Valley. In 1761 a German potter had a pottery wheel and all the equipment shipped from Philadelphia to Winchester, VA and it arrived in perfect condition, and new settlers were arriving during that time.