im know the great lakes waters hold some monster pike. Niagara river, st lawrence river. so its not just up north. a couple years back i saw a 10 year old kid catch a 40 off the bronte peer.
I would say that if there is an abundance of bait fish then pike can get big in many rivers and lakes. Not sure exactly the genectic make up of pike but you think, southern pike would have a larger growing season??? like bass for example?
cheers!