1796 Bernard McMahon Opens a Seed Store In Philadelphia Timelines: Timeline of American Garden History
McMahon (also written as M’Mahon) was an international seed trader famous for preserving seeds brought back from the Lewis and Clark expedition and supplying buyers such as Thomas Jefferson.
Hobhouse, Penelope. “The Development of North American Horticulture,” Plants in Garden History. (London: Pavilion Books, ltd, 1992),