>>2430331The night sky's brightness is measured through magnitude per arc second squared, or mag./arc sec2—the lower the number the brighter the sky.
For the milky way to be visible at all at the zenith, the sky must be at the brightest 20.2 mag/arc sec2. The highest that is generally recorded is 22.00 mag/arc sec2 and considered a perfectly dark sky, Manhattan in NYC at night has about a 17.66 mag/arc sec2.
These values are used to determine a placing on the Bortle scale, which numbers 1-9, 1 being a perfectly dark sky, 8-9 being an inner city sky.
Usually, the sky has to measure at least a 4 (20.49-21.69 mag/arc sec2) to see the milky way with the naked eye.
Other factors come into place, mainly the moon cycle. You won't be able to see much with a super moon out, that's why any nights you plan on stargazing need to be less than half full, preferably a new moon. Night vision also affects it. Let your eyes adjust and don't look at any artificial lights, over the course of half an hour you will be able to see the most visible stars.
As for east coast gazing, Maine, Appalachian West Virginia, and rural New York are the best. Maine is the only place west of the Mississippi River in America where you can see a perfect dark sky. WV and NY have places that are above 21.9 mag/arc sec2.
National forests that are a few hours away from the nearest big cities are generally ok for stargazing. Low population areas usually have less light pollution as well. Use
https://www.lightpollutionmap.info/ to see what's nearby.
