Teddy Roosevelt and John Muir on Glacier Point, Yosemite, 1903. Theodore 'Teddy' Roosevelt (1858-1919) was the 26th President of the United States (19011-1909). He is noted for his exuberant personality, range of interests and achievements, and his leadership of the Progressive Movement, as well as his cowboy persona and robust masculinity. He was a leader of the Republican Party and founder of the short-lived Progressive (Bull Moose) Party of 1912. Before becoming President, he held offices at the city, state, and federal levels. Roosevelt's achievements as a naturalist, explorer, hunter, author, and soldier are as much a part of his fame as any office he held as a politician.