By 1760, according to Scott Paul Gordon, Henry had largely abandoned his occupation of gunsmith and had become a successful ironmonger and merchant in Lancaster.
In 1780 Henry informed Joseph Reed that he had "laid out…between Sixty & Seventy Thousand Pound" just to "purchase Leather and Paying Workmens Wages at the Shoe-Factory[s]" he had established "at Philadelphia, Allentown and Lancaster.
Henry was an intellectual who helped found Lancaster's Juliana Library-Company in 1759, which during the Revolution and after was housed in his residence, and he held membership in the American Philosophical Society in Philadelphia, whose first Transactions (1771) printed Henry's account of his invention of a "Description of a Self-Moving or Sentinel Register" to regulate the flue of a furnace.
Henry invented a screw auger, manufactured and sold exclusively at his Lancaster store, and some credit him with inventing the steamboat: the twelve-year-old Robert Fulton, a Lancaster neighbor, visited Henry in 1777, who had been experimenting since 1763 on boats with steam engines on the Conestoga River (Fulton's own experiments began only in 1786 in England).
Henry's sons carried on his gun business, in Lancaster, in Philadelphia, in Nazareth, Pennsylvania, and then in Boulton, PA. One of his sons, John Joseph Henry, served as a sixteen-year-old rifleman on Benedict Arnold's march on Quebec in the fall and winter of 1775 (he was captured and imprisoned for much of 1776), and later served as president judge of the second District in Pennsylvania from 1795–1811.