Seems like there may be far and few but is there places around to boondock in the NJ, PA, NY and north to Maine area? Maybe some folks don't want to give up there favorite spots than maybe just a yes or no with a general discription would give some confidance that we can get lost on purpose in this area!
Check online for national and state forests in the areas you're interested in. They often allow camping outside of developed campgrounds under certain restrictions. Then contact the ranger station for information on dispersed camping. They can point you in the right direction. Have fun.
You won't have any luck in the White Mountain NF as camping outside of the campgrounds is not allowed and longer.
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There are some places, as you say they are few and far between, however the internet is not the place to mention them. It would be like telling someone where your special fishing spot is, in a few years it'd be overrun then ruined. I know of some in Me. NY. NH. and Vt. Some require you to check in, some don't. All are legal.
Bob & Deb
W Ma.
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