Margaret O'Neill (Peggy O'Neill), c.1796–1879, wife of John Henry Eaton, U.S. secretary of war under President Andrew Jackson. She was the daughter of a Washington tavern keeper and married John Timberlake, a purser in the U.S. navy. After his death, she became (1829) the wife of Eaton, who soon afterward entered the cabinet. The wives of the other cabinet members refused to accord her social recognition because of the alleged intimacy between Major Eaton and Peggy O'Neill before their marriage and because of her humble birth. President Jackson, a close friend of Eaton, tried in vain to ensure Peggy Eaton a place in society. The attempt almost disrupted the cabinet and worsened the relations between the President and the Vice President, John C. Calhoun, whose wife was a social leader. As a result, Jackson transferred his favor to Martin Van Buren, who as a widower was better able than others to recognize Mrs. Eaton. She was well received at the court of Spain, to which her husband was appointed minister in 1836, and was a social favorite in London and Paris. Her maiden name is also recorded by historians as O'Neale and O'Neil.
See biography by L. Phillips (1974).