There's 50 of them, and D.C. too... What character would you write to represent any given State? (D.C.) too. I've always thought of a vampire pencil cartoon with a big smile greeting people in Pennsylvania... Draw a big poster of him (it's a he) and have him smiling next to the Welcome To Pennsylvania sign greeting people into PA. The Pennsylvania Pencil you could call him and he'd be a vampire. IDK. IDK, something I came up with in one second flat when I first heard the word Pennsylvania when I was child, before I ever went there (I've been twice) and... Yeah, great state, great people, what's not to love?
For D.C., I would have an Enclave Soldier, proudly displaying his plasma rifle, and under his boot, the skull of a super mutant.