I'm posting this because there might be a small chance that you live under a rock and my blog is the only news source you read, lol.
I found this to be crazy interesting! Apparently the only presidents to have done this are Theodore Roosevelt and Woodrow Wilson. Jimmy Carter won, but he wasn't in office at the time. I love being alive for historical events! (Positive ones, that is... I'll pass on being alive for WWIII!) Here's one of the articles I read about it on People.