A green dragonfly in the Fan

I accidentally noticed this beautiful emerald green dragonfly in our front yard in the Fan, Richmond, Virginia. It was very calm and tranquil so that I could rush back home to grab my camera and be back in time to take a good shot. I actually like this combination of emerald green with green background and a few black spots on dragonfly's tail (I'm not sure it's called "tail" though). I wish someone could tell me how this beautiful creature is called!