Presidency of Theodore Roosevelt
Theodore Roosevelt's tenure as the 26th president of the United States began on September 14, 1901, and expired on March 4, 1909. Roosevelt, a Republican, took office upon the assassination of President William McKinley, under whom he had served as vice president, and secured a full term in the 1904 election.
Source: Wikipedia — Presidency of Theodore Roosevelt (CC BY-SA 4.0)