Defunctland is a Youtube channel that does highly interesting documentaries on, among other things, amusement parks and attractions. A few months ago, he did one on Kennywood's biggest mistake. It was amusing how a guy whose career is talking about amusement parks and the relationships that locals have with them, was clearly a bit weirded out by how strongly Pittsburghers feel about Kennywood. Still, of the 10 oldest roller coasters in the country, 5 are in PA and 3 are at Kennywood. Whatever the park's current faults, I still find it really cool that my 5yo daughter can enjoy the same attractions that her great grandparents rode at her age.

(All in all, though, I prefer Idewild.)

EDIT: I totally forgot that the Old Mill that is the focus of the video dates all the way back to 1901, a generation older than the roller coasters. My daughter's great great grandparents may have ridden it as small children.