The federal censuses of the Town(ship) of Mohawk, Montgomery County, NY, record your Adam Fonda in 1860, 1870, and 1880.
In 1860 he is listed as a farmer, aged 20, in the household of Lydia Fonda, aged 54.In 1870 he is a merchant (flour and feed), aged 30, and head of a household which included Maria C. Fonda, aged 24, who was born in Vermont, and Lydia Fonda [undoubtedly his mother], aged 62.Adam's personal estate was valued at $5000.
In 1880, aged 40, he was a clerk in a store with wife Maria C. aged 34, children Laura, 9, Adda, 7, Girtie, 5, Josephine, 4, and Alexander, 2.Also in the househod was Laura Hill, mother [presumably of Maria C.], widowed, aged 52, born in NY; Rosa Oathout, 17, servant; and Michael Leonard, 24, laborer, b. in Ireland.
According to records of the Reformed Church of Fonda, Adam, aged 71, was buried 11 May 1911.The funeral was at the house and attended by Rev. Henry C. Cussler.
I have a note that Adam, son of Adam Fonda, was baptised at the Reformed (Dutch) Church of Fonda on 3 March 1841, but I regret not being able to confirm this.