Correspondence; letterbooks; diaries; nine volumes of writings including his autobiography, notes on the proceedings of Congress, and transcriptions of essays, poetry, and extracts from various sources; and other papers relating to Plumer's political career, writings as an essayist, and personal affairs. Subjects include New Hampshire history, politics, courts, and state militia; New England politics; relations with the Barbary States, France, Great Britain, and Spain; the Louisiana Purchase; the purchase of Florida; and the Federalist Party (Federal Party). Other subjects include the Dartmouth College controversy, impeachment cases of judges Samuel Chase and John Pickering, agriculture, education, government, international trade, paper money and the public debt, politics, and religion. Family correspondents include Plumer's wife, Sarah Plumer; his son, William Plumer, Jr.; and his brother, Daniel Plumer. Other individuals represented by correspondence or subject matter include John Adams, John Quincy Adams, Aaron Burr, Henry Clay, Charles Cutts, John Farmer, John Taylor Gilman, Salma Hale, John Adams Harper, Isaac Hill, Thomas Jefferson, John Langdon, Arthur Livermore, Edward St. Loe Livermore, Jeremiah Mason, Jacob Bailey Moore, Nahum Parker, James Sheafe, Jeremiah Smith, and Levi Woodbury.