Last night I cut through my own tangle of confusion and carelessness and finally discovered the birth of my ancestor, Martha Bennett White O'Brien. I have had pieces of the answer, and in fact, the answer itself, for years but never saw it clearly until I decided to hack away at the thicket of information one more time and suddenly things clicked.
Martha Bennett's first husband was Ebenezer White. He was a mason who worked in the black granite quarries on Isle La Motte. Their children were born between 1818 and 1824 and Ebenezer died in February or March 1827.
The first problem was that my grandfather's genealogical record "Ancestors and Descendants of Orville C. Baker" stated Martha's father to be John Bennett of Augusta, Maine. The second problem was that Martha's gravestone giving age at death, extrapolated to a birthdate of 18 November 1804. Compounding the error was the fact that her age was never accurately stated for a census. In 1820 when she was with her first husband in Vineyard, now Isle La Motte, Grand Isle, Vermont, she was in the age range to have been born between 1794 and 1804. In 1850 she was reported as 40 years old (i.e. born about 1810) and in 1860 she was recorded as being 54 years old (i.e. born about 1806). She was not found in 1830, 1840 or 1870 despite the fact that she died in 1872.
The next problem was that her first child was born in June of 1818. Believing that Martha was born in 1804 led to the erroneous conclusion that she became pregnant at the age of 12 and gave birth at the age of 13, a troubling idea even by the standards of an earlier age. The details of how I looked high and low for her birth in all the wrong places is no longer interesting. Suffice it to say that because I knew she had a family connection to a woman named Rachel Bennett Woodard Carron; a Bennett who also came to Grand Isle from Maine, I looked once again at Rachel's parents and family. There for the first time I saw that she had a sister named Patty, a well established nickname for Martha, and that sister was born on 18 November, not 1804 but 1797. This is proof enough to me that my Martha was Rachel's sister Patty, daughter of Nathaniel and Dorcas (Wharff) Bennett, born in New Gloucester, Maine. It is also worth noting that Ebenezer and Martha named their first daughter Martha after her mother and their first son Ebenezer, presumably after his father. They named their second son Nathaniel Bennett White.