There is extensive material on the Manahan family in the History of Hillsborough, NH vII - Genealogy by G Waldo Browne.
"Under different forms of spelling this is an old and honorable family in Scotch history ..."
"Michael Manahan born in the north of Irelandabout the time of the exodus of the Scotch-Irish to New England."
"Adam, second son of Michael Manahan, b. in (Northern) Ireland about 1760?, came to New England at the close of the Revolution in search of his brother John, from whom nothing had been heard since his desertion from the Army."
John, eldest son of Michael b.1744, was sent with a body of troops to Quebec - newly acquired by England from France. Fled with others to New England. He settled in Londonderry, NH where there was a large settlement of Scotch-Irish from Northern Ireland. There is an interesting account in Browne about John and the reunion of the brothers.
William Henry M. youngest child (of 8), after marriage to Fannie Harriet Chafin of Walpole, NH, settled in Hillsborough, NH and became a prominent citizen of the town. He was best known as an auctioneer of real estate.
Wm. H. M.,Jr. after education as photographer, purchased a local photo studio in 1899 and continued that enterprise until his retirement in 1953. The photo studio continues to this day under other ownership. The original studio was in business as early as 1868. The negative collection from the studios was given in 2002 to the Hillsborough Historical Society.