Post was born near Westbury, New York on April 4, 1771.
[2] His older brother was Dr. Wright Post, a professor of surgery and anatomy at Columbia.
[1] He studied medicine, but did not practice, instead, he engaged in the drug-importing business in New York City.
[1] On August 10, 1792, Post was married to Magdalena Blaau in New York City.
Together, they had eight children, including:[2] After the death of his first wife in 1811, Jotham married Julia Strong on October 2, 1815 in Albany, New York.