So we have a dragonfly. By the apparent large size, striped thorax, spotted abdomen, and vertical hanging, it’s one of the darners. We can eliminate Common Green and Comet by the lack of a solid thorax, Springtime, Harlequin, and Taper-tailed by date. Swamp and Cyrano have a more ringed appearance. Spatterdock has bright blue eyes. That leaves the genus Aeshna, of which there are quite a few in Massachusetts.
We can eliminate Mottled on thoracic pattern right away but several others are close. However, looking at the appendages we can see that they are fairly expanded and paddle-ish. Only Lance-tipped and Shadow match those. Lance-tipped is eliminated by the thoracic pattern, which would be more jagged. Shadow normally shows thin stripes with a slight triangle extending from the rear of the front one, which this one shows.
Shadow Darners are among the most common darners, especially late in the season. In fact, after the first week or two of September, I assume it’s a Shadow unless otherwise. They’re relatively darker than most others and often fly very low to the ground, which makes them much easier to observe. They can fly quite late (I just had my first November record the other day, so they may still be out there now).