Amy GreenbergAmy S. Greenberg is George Winfree Professor of History at Penn State University. She is the author of five books, including A Wicked War: Polk, Clay, Lincoln and the 1846 U.S. Invasion of Mexico (Knopf, 2012), Manifest Destiny and Aerican Territorial Expansion: A Brief History with Documents (Bedford/St. Martin's, 2012), and, most recently, Lady First: The World of First Lady Sarah Polk (Knopf, 2019). Read More Read Less