Biography: Theodore Roosevelt Jr. (October 27, 1858 – January 6, 1919), also known as Teddy or T. R., was the 26th president of the United States, serving from 1901 to 1909. Roosevelt previously was involved in New York politics, including serving as the state's 33rd governor for two years. He served as the 25th vice president under President William McKinley for six months in 1901, assuming the presidency after McKinley's assassination. As president, Roosevelt emerged as a leader of the Republican Party and became a driving force for anti-trust and Progressive policies.