The night sky note for Sept. 19, from the Abrams Planetariumat Michigan State University states the Harvest Moon is the full moon closest to fall's first day.
It was full Thursday morning at 7:13 a.m. EDT.
The Huffington Post tells us that the "annual celestial sight was dubbed the "Harvest Moon" because its light allowed farmers in the Northern Hemisphere to harvest their crops for several hours more into the night, the Farmers' Almanac notes."
And the website EarthSky tells us this general information about full moons:
"No matter where you are on Earth, this full moon – and every full moon – ascends over your eastern horizon around the time of sunset. It’s always highest in the sky in the middle of the night, when the sun is below your feet. That’s because a full moon is opposite the sun. Being opposite the sun, the moon is showing us its fully lighted hemisphere, or “day” side. That’s what makes the moon look full."