Hmm, it sounds like a tough spot, possibly too much shade for an evergreen. A Serviceberry tree might survive, although they can be finicky.

Are there any smaller (understory) trees currently coexisting with the maples on other parts of the property? If so, planting the same type of tree in your clearing might work.

Eastern Hemlock (Tsuga canadensis) does fine is shade, tolerates competition from other trees pretty well, and is probably your best bet. With partial sun you'll get a great-looking tree that should have a nice pyramidal form. Helocks are most common in shady, moist ravines, but are also common in drier woods. Also, it is the PA state tree.