When I learned that there are close to five hundred “dragonflies” in the U.S. and no good available source to identify them, I settled for the occasional picture. Below is an easy one, however, called the Twelve-Spotted Skimmer. Very common here.
Blue Dasher (Pachydiplax longipennis).
Widow Skimmer (Libellula luctuosa)
American Ruby Spot Damselfly.