This katydid was on a parked car in Wildwood Crest, New Jersey. After keying it out as best I could with this guide (and photos on BugGuide), I think it is an anglewing katydid, in the genus Microcentrum. In New Jersey, it could be either a Great Anglewing Katydid or a Lesser Anglewing Katydid.
This one appears to be a nymph because the wings are not fully grown. Despite being a nymph, this individual was not small, with its body (not including legs or antennae) being a little under two inches long.
From what I have read, one can distinguish the two species by the color of an individual's stridulatory field, but I am not sure if that is reliable for a nymph.