Simon Nathan was born in Frome, England, and was the first of his family to come to America. He arrived in 1773 and established himself as a merchant in New York. With the outbreak of the Revolution, Nathan responded to the entreaties of Virginia governor, Thomas Jefferson, for interest-free loans to outfit soldiers at Fort Pitt. It was an act of generosity from which he would never entirely recover financially.

Meanwhile, Nathan had fled New York for Philadelphia, as had so many supporters of the American cause. It was there that he met his wife, Grace Mendes Seixas, who along with her family had also abandoned New York for Philadelphia. While there he served two terms as parnas of congregation Mikveh Israel where Grace’s brother Gershom Mendes Seixas was temporarily serving as hazzan.

After the revolution they moved back to New York where Simon set up an auction house. He maintained his level of activity with the Jewish community, serving as parnas of Shearith Israel four times. Their only son, Seixas, was born in 1785.