Well Taffy, there is no real "magic" - at least the way one typically thinks of magic and it is based on a myth. The common myth of the hex signs on the barns of the Pennsylvania "Dutch" is that they were to ward off evil spirits. The simpler and apparently more correct explanation is that they are just decorations (The Story of the Hex Sign). If you want to see what hex signs look like, here is a link to an online hex sign catalog of a place I occassionally drive by in the town of Paradise: The Hex Place.

They are pretty cool to see on a barn and one of the things that gives some character to this part of Pennsylvania. BTW, I'm guessing the reason you think PA is creepy, is because it sounds similar to Transylvania - though I'm sure some of the odd news stories about PA folks posted in the Backroom this past year has helped with that creepy feeling you are getting.