I have traced my GG maternal grandfather to his birth in 12 Dec 1837 in Milton, Strafford, New Hampshire, United States. He was adopted by the Peter and Adah Elder Family of Windham, Cumberland, Maine, United States at about 5 years of age. He was born J Edwin Smith, from what I can tell (other published info) although I've found no birth certificate to date.
The Elder family adopted a number of children from various locations during their lifetime as Mrs. Elder could bear no children.
My question is does anyone have any recommendations on how to pursue discovering his parentage and/or origins prior to his adoption?