John S. March was born in Middletown, Orange, New York, in October of 1861. He was the son of an Englishman, Thomas Alfred March (b. 1835), who was employed as a saw maker. His mother was an American named Jane (Jennie) Harriet Mills (b. 1837). His father, who had been born in London, came to America as an infant. John's parents married around 1860. They had one other known child, John's younger sister Sarah Isabell (b. 1864). Sarah was known as Belle.