The coloring was as you see it, black and shiny, not speckled or hairy. Looked like patent leather.

but this is clearly C. viridipilis.

I'm an amateur so I will take your word for it.

The closest match I found was Chalcolepidus viridiplis, but not close enough since it isn't hairy (and certainly not greenish hairs). Dicrepidus palmatus combs were too long.

The beetle was on a tree,perhaps a sumac or a locust tree. The tree was dangling from a cliff over the water along the Western Shore of the Chesapeake Bay. The water is very shallow so the only way to reach this area is by walking in the water. The area is quite rural and these particular cliffs are not easy to access by land or boat. The evening was hot and humid with little breeze. The tree was full of other creatures, but none seemed to have any interaction with this beetle.

The beetle seemed to know that I was taking its picture, as it waved its antennae at me when I got a little too close. The rest of its body remained perfectly still. I took pictures of the beetle over the course of 12 minutes shortly before 7 PM when I returned to shore. It did not move at all other than its antennae waving.