Long Island Plantation info needed.

  I  am researching Joseph Dunham who lived in St Andrews NB and St George NB from 1790-ish to 1830-ish.   I believe this Joseph Dunham may be associated with the Dunham's of Deer Isle, Maine.

   I found that one of Joseph's sons states that his father was born in "Long Island"  - which was interpreted to be "New York".   But some of the islands around Deer Isle, ME were, at that time, known as Long Island Plantation.   Isleboro was known as  Long Island at the time of Joseph's birth.

   Can anyone tell me what islands comprised Long Island Plantation in the mid to late 1700s?

Thanks,

Jeff