Wow....Indiana once had over 600? I don't know how many PA once had....but I think we have about 200 still standing. The most interesting one I've read about is the Wrightsville Ferry bridge crossing the Susquehanna River (Lincoln Highway). It was rebuilt a bunch of times....but I think it was the longest covered bridge in the world until the army torched it in the civil war to keep the confederates from crossing? It's a concrete arch bridge now.
http://en.wikipedia.org/wiki/Columbia-Wrightsville_Bridge
Cool stuff, I love reading about these old bridges - and yeah, I know a lot of amish around here head out there and ohio to visit family. Several Walgamuth's around here too.