Ok, granted I don't know much about wildlife in PA, his tiny ears make me think he's domestic. BUT take into consideration that:

1. I've only seen one baby cottontail in my life...and I was about 6 yrs old.
2. I'm in NM and I'm used to seeing jack rabbits (ie HUGE ears lol).

Being the sucker that I am (and as I often let my heart rule my mind) if he let me touch him, I'd take him in in a heartbeat.

Have you tried to contact a wildlife rescue/rehabiliation organization?

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Forgot to add that, while he looks so tiny, he's probably able to make it on his own. (I'd still call a wildlife org. just to make sure though. They can relocate him to a safe place. )