In 1828 Franklin formed a partnership with his nephew John Armfield when Isaac's father James died and bequeathed land and slaves to him and his brother James. They set up Franklin & Armfield in Alexandria, Virginia (then part of the District of Columbia). Between 1828 and 1837, Franklin & Armfield became "the largest slave trading firm" in the United States. Franklin also had offices in New Orleans, the major slave trading center in the South, St. Francisville, and Vidalia, Louisiana. Franklin admitted in letters to raping some of the women he bought and sold as slaves.