Theodore Gerrish (20th Maine/Civil War)

Greetings to all from the Pine tree State! My mother's second uncle was Theodore Gerrish, 1844-1923. I'm trying to fill in some of the gaps in his life from the time of his birth to the time he enlisted in the Army to fight in the Civil War. Here is what I've been told by the State of Maine:

"Our collection of Civil War photographs is almost
exclussively of Officers.We have no photograph
of Theodore Gerrish.

Our Adjutant General's Office Records includes an
alphabetical card index of all of the 70,000+ men who
went in to the Maine Volunteer Civil War Regiments.

Theodore Gerrish enlisted as a Private in Co. H, 20th
Maine Infantry, on July 21, 1862.At enlistment, he
was 18, single, with light complexion, blue eyes, light
hair, a farmer and stood 5 ft. 11 in. tall.He was born
in New Brunswick and resided in Falmouth, Maine.He
was mustered out and honorably discharged on June 4,
1865 "in the field".

His Graves Card shows he was born in 1846 and that
Rev. Theodore T. Gerrish died at Summertown, Tenn.
on Feb. 9, 1923 and is buried in Evergreen Cemetery
in Portland, Maine."

Another source gives conflicting information about his place of birth, saying that it was Oakfield, Maine (my mother's hometown). Have any of you information that might clear any of this up?