Beginning during the Spanish involvement in the American Revolution, he performed personal favors, such as making deliveries for Francisco Rendón and providing a house for ambassador Josef de Jáudenes [es].
[4][5] Merchants like Leamy "exhibited extreme flexibility in business dealings, including the willingness to ship provisions by indirect routes, to pay off corrupt bureaucrats, and even to transport slaves to gain admittance to ports that were officially closed."
[12] By passing on secret information from peninsular Spain to the colonies, Leamy acted similarly to a consul, though he held no diplomatic title.
Primarily he exported flour, bringing on average 2,000 barrels per voyage to Cuba, and returning to the United States with gold and silver specie.
[14] After a temporary lifting of trade restrictions, on November 28, 1798, Leamy's frigate John arrived at Montevideo carrying lumber, becoming the first United States vessel to enter the Río de la Plata.
[18] Compared to the early years of success, Leamy's business was stymied from 1802 to 1807, the time Valentín de Foronda [es] spent as Spain's consul-general in Philadelphia.
[24] He also used his merchant wealth to gain prominence in the Roman Catholic community, donating $200 to the original construction of St. Augustine Church in 1796—the largest individual contribution.
[34] After his death the Leamy children used it as a summer home until Ann and Elizabeth donated the land to help establish the Episcopal Hospital in 1852.
While historian Charles Lyon Chandler wrote that two days later he was buried in the cemetery at St. Mary's,[21] he is also recorded as being interred with his children at St. Paul's Episcopal Church.
[1] In 2003, Linda K. Salvucci concluded that "he was the most prominent American trader with the Spanish Empire of his generation, but John Leamy's significance has eluded students of Philadelphia's postrevolutionary commerce."