Majik Man, they are definitely as far north as Oil City...I know the dam is still a ways up river....but, not far fetched for them to be up there. In the upper Allegheny, they are found in the deeper areas of river.
I don't know if you'll find 30+lb fish up that far..but I'd bet you'd find smaller ones....they seem to be ever expanding and it seems like the newer generations are growing much quicker than the fish did 15 years ago... at least in the Ohio and out east in the Susquehanna. They say the Ohio has been cleaning up and that's whats allowing the fish to grow quicker..
They are in more places than people realize.
Unlike channel cats and bullheads, they typically won't hit stink baits, liver, soap, hot dogs etc. Fresh cut bait or live bait for flatheads...which is why you don't see many as accidental catches.
Their appetite is usually big. That is an average-large sized bluegill stuck in it's mouth. My hook actually never made contact..it stayed in the live bluegill and was lodged hard enough to endure the fight.
Panfish, suckers, big creek chubs etc work well.
I caught my first, about that size, on a couple big night crawlers...that was a good 15 years ago...I've been addicted ever since...that's really the only fish I Target now... everything else is bait lol.
Best way to see if they are around is to go fish for them. They can be frustrating. Right now they are on spawn and extremely difficult to catch..it's starting to tail off and fishing is picking up by the day. Couple more weeks and it'll be better... april-may and Sept-oct are probably the best months. The spawn lasts around 6 weeks. Obviously not every fish spawns at the same time..but after the spawning activities, the males guard the nests and keep the fry safe a good while..
Post spawn fish are usually best up pretty good.