Theodore Roosevelt was the 26th President of the United States, serving from 1901-1909. Theodore Roosevelt, at 42 years old, became the youngest President in U.S. history when he took office following the assassination of William McKinley. While campaigning in Missouri, Theodore Roosevelt accepted an invitation to fly in an airplane piloted by Arch Hoxsey and so, on October 11, 1910, he became the first American President to fly in an airplane. Theodore Roosevelt unsuccessfully ran for reelection in the Presidential race of 1912 on a Progressive or "Bull Moose" Party ticket, a party formed by Roosevelt after he lost the Republican nomination to William Howard Taft. Theodore Roosevelt died in 1919 at the age of 60.