Three U.S. Presidents have been awarded the Nobel Peace Prize while in office. As of 2017, one former president has been awarded the prize, Jimmy Carter in 2002 for his “decades of untiring effort to find peaceful solutions to international conflicts”.

The first sitting president to be given the award was Theodore Roosevelt in 1906 for his role in mediating the end of the Russo-Japanese war. The defeats of the Russian army and navy coupled with the 1905 Russian Revolution brought them to the negotiation table and had Theodore Roosevelt mediate the talks. The Treaty of Portsmouth was signed on September 5, 1905, bringing the war to an end.

Woodrow Wilson was the second sitting president to receive the award for “his crucial role in establishing the League of Nations”. The League was formed after World War I, with the intent for settling international disputes to hopefully prevent a catastrophic war from occurring again. Wilson received the award in 1919. Ironically the United States never joined the League.

The most recent sitting president to receive the award is Barack Obama in 2009 for “his extraordinary efforts to strengthen international diplomacy and cooperation between peoples."

More Info: en.wikipedia.org