What is now the township of Pittsburg, NH was at one time an idependent country, a country that formed decades after the revolutionary war, and which was only reannexed when the citizens of that country asked to be. This township was called the Republic of Indian Stream, and you can read Daniel Doan's book on its history. Indian Stream was formed not out of a grant by a european sovereign, but from a grant by the St Francis indian chief known as "King Phillip".
Similarly, what is now Vermont was once part of NH. Ethan and Ira Allen and their compatriots formed their own state after the revolution and their ratification of the US Constitution was only accepted by the Congress after Vermont agreed to return to NH jurisdiction a number of towns on the east bank of the Connecticutt that had voted for secession along with the rest of Vermont.
So the picture for political secession in the twin state area actually has a pretty well known and peaceful history. Things only came to blows in Indian Stream when Canada was going to invade and annex it.