Barack Obama is not the only one. The other US Presidents who have won the Nobel Peace Prize are, in chronological order, Theodore Roosevelt, Woodrow Wilson, and Jimmy Carter. (You can watch President Obama's remarks here).
Theodore Roosevelt was the first American to won a Nobel in any category. His Peace Prize was for his work in helping broker the end of the Russo-Japanese War in 1905.
Normally, a US Secretary of State would have handled such diplomatic chores. But Roosevelt’s Secretary of State, John Hay, died in July 1905, and the forceful TR took charge of the duties himself.
Roosevelt invited diplomats from the warring parties to his home at Sagamore Hill on Long Island to begin negotiations. Both sides were looking for peace -- the Russians had suffered military setbacks, and the Japanese were in financial trouble.
Roosevelt did not pick up his Nobel medal, or his prize money, until 1910. He said he did not feel right accepting them while in office.
Woodrow Wilson won the Nobel Peace Prize in 1919 for his services in establishing the League of Nations.
Following the tragedy of World War I, Wilson decided to lead the US peace delegation personally. He traveled to Paris in 1919 to press his idealistic vision of a world united against war.
While the peace treaty itself did not reflect all the magnanimity of his famous “Fourteen Points” in support of peace, he did secure the adoption of a covenant for a League of Nations, a precursor to today’s UN.
He barnstormed around the US in the months that followed in an effort to push ratification of American membership in the League through the Senate. But the strain of the effort resulted in a stroke that robbed him of his health. In the end, the US did not join, as ratification was defeated.
Jimmy Carter is the only president to have won the Nobel following his time in office. His was awarded in 2002, for “his decades of untiring effort to find peaceful solutions to international conflicts, to advance democracy and human rights, and to promote economic and social development,” in the words of the Norwegian Nobel Committee.
Many commentators at the time felt that the award was in recognition for a man who appeared to have redefined how much an ex-president could accomplish.
Carter previously had come close to winning the Peace Prize in 1978 for his efforts in bringing together Israeli Prime Minister Menachem Begin and Egyptian President Anwar Sadat to sign the Camp David Peace Accords.