In his illustrious racing career the great Man o' War won all of his horse races except one, the Sanford Memorial Stakes, where he lost by a neck. What was the name of the horse that beat him?

In the early 1900s, there were no starting gates. Horses circled around and then lined up behind a piece of webbing known as the barrier and were sent away when it was raised. In Man o' War's only loss, the Sanford Memorial Stakes, he was still circling with his back to the starting line when the barrier was raised (though some accounts say he was turned only slightly sideways). What is undisputed is that Man o' War had a terrible start, and the normally front running colt found himself far behind the other starters. Jockey Johnny Loftus then put Man o' War in a bad position, getting boxed in by other horses. Despite this, he came close to winning, losing only by a neck while conceding 15 pounds to the horse who beat him. The winner was Upset, whose name is sometimes erroneously thought to have popularized a new phrase in sports (meaning an underdog beating the favorite)—in fact, the term "upset" was already in use to describe such a situation decades before.