Theodore Roosevelt Jr. (October 27, 1858 – January 6, 1919), often referred to as Teddy or T.R., was an American politician, soldier, conservationist, naturalist, and writer who served as the 26th president of the United States from 1901 to 1909. He was previously active in New York politics and served as the state's 33rd governor for two years. He was the 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.