I have always heard that, counting freshwater, Minnesota has more coastline than any other state by a wide margin. (I 'spose I'm open to being convinced that Michigan has more - I usually hear this stat from my MSP-based in-laws.)

Counting only saltwater, I simply can't fathom it being anything other than Alaska. Even if islands starting throwing a wrench in things, it seems that Alaska should still be able to hold its own with the Aluetians, etc.