The closest in appearance that I found in “A Guide to North American Bees: The Bees in Your Backyard” by Wilson and Carril is the Xylocopa Apidae. This one is entirely black, so I believe it is a female. Heavy load of visible yellow pollen appears on both of the rear pointing legs. It is sitting atop the cone flower where it has exhibited flower constancy over several days. I have since observed two additional such bees at the same coneflowers.