My guess is that it was glued up there with some sort of construction adhesive. If that is the case, removing it without some damage to the wall will be near impossible. Use a stiff putty knife to do your best at prying it off the wall. You can use that same putty knife to try and scrape away any remaining adhesive. Use drywall joint compound the skim smooth any damage to the wall.
Thanks! I appreciate the advice!
No problem, let me know how it goes for you. Good luck!
Try to loosen the top edge gently and get a large piece of wire picture wire...wear gloves and gradually work your way down with a saw-like left to right motion while bearing down on the wire.....should work
HandyANDY, that sounds like a great idea! Thanks! Will let everyone know how it goes!