In 1868 he married Harriet Wheaton.
An Irishman, Gamble probably emmigrated to the USA in the late 1840s. He worked as a clerk in the offices of his brother-in-law Samuel Wann in New York. He lived for some 20 years at Staten Island, NY. By 1872 he had a home in the Highlands. He was a pious man who formed a close friendship with AMW (16 years his senior). They probably met through Ann Maxwell, a common acquaintance from Scotland at the 'Henderson Home,' Herkimer Co. (see Cruger, H.).