It's a common green darner dragonfly, the Washington State Insect. Its top speed on the straightaway is at least 30 mph and some persistent person determined that one could fly 85 miles in a single day. I checked the leaf later with a ruler, and it must have stretched four inches from nose to tail.
Using a macro setup, I crept as close as I could and snapped its portrait:
Normally bugs don't let me get this close, but maybe its size gave confidence. Here are facets on its eye: