Though the U.S. separated from Great Britain nearly 250 years ago, the two countries are the closest of allies. Queen Elizabeth is a big reason for that. She met with 13 American presidents during her reign of 70 years. The first was Harry Truman. With us now to discuss the relationship between Queen Elizabeth and American presidents is historian Barbara Perry, Director of Presidential Studies at the University of Virginia's Miller Center and co-director of the Presidential Oral History Program.