James Winthrop was the son of physicist John Winthrop. He graduated from Harvard in 1769, and was wounded at the Battle of Bunker Hill. He was librarian of Harvard from 1772 until 1787. For several years, he was a judge of the court of common pleas, and for a long time register of probate. He was part of the anti-federalist movement. He bequeathed his library to Alleghany College in Meadville, Pennsylvania.
- Attempt to translate the Prophetic Part of the Apocalypse of St. John into Familiar Language (Boston, 1794)
- Systematic Arrangement of Several Scripture Prophecies relating to Antichrist (1795)
- Attempt to arrange, in the Order of Time, Scripture Prophecies yet to be Fulfilled (Cambridge, 1803)
He also made scientific and literary contributions to current literature. He was the speculated author of the Letters of Agrippa (November 1787-January 1788), which appeared in the Massachusetts Gazette.
- Wilson, James Grant; Fiske, John, eds. (1889). "Winthrop, John". Appletons' Cyclopædia of American Biography. New York: D. Appleton
- "Anti-Federalist Papers: Letters of Agrippa, I-XI". Constitution.org. Retrieved 2011-12-10.