John Moore, Jr., was the only son of John Moore, Sr. (1751-1836), a Boston mariner, and his wife, Alice Niles. John Moore, Sr., was born a free black in New York City and moved to Boston as a young man. He supported the patriot cause during the Revolutionary War and, according to family history, fought at the battle of Lexington. After the war, the elder Moore worked as a house servant in Nova Scotia before earning a seaman’s certificate. In 1784 he retired from the sea and settled permanently in Boston, where his son John, Jr., was born about 1800.