Christopher Klein (christopherklein.com) is the author of When the Irish Invaded Canada: The Incredible True Story of the Civil War Veterans Who Fought for Ireland’s Freedom and Strong Boy: The Life and Times of John L. Sullivan, America’s First Sports Hero. He is a frequent contributor to History.com, the website of the History Channel, and has written for The Boston Globe, The New York Times, National Geographic Traveler, Harvard Magazine, Smithsonian.com, and AmericanHeritage.com.