McKinley and Roosevelt won the presidential election of November 6, 1900 against William Jennings Bryan and Adlai E. Stevenson Sr., and they were inaugurated on March 4, 1901. Roosevelt was the second youngest U.S. vice president (John C. Breckinridge, at 36, was the youngest) at the time of inauguration. Roosevelt found the vice presidency unfulfilling and thought he had little future in politics, and considered returning to law school after leaving office. On September 2, 1901, he first uttered a sentence that would become strongly associated with his presidency, urging Americans to "speak softly and carry a big stick," during a speech at the Minnesota State Fair, not knowing that twelve days later, he would be catapulted forever into the public consciousness.
McKinley was shot on September 6, 1901, and died September 14, vaulting Roosevelt into the presidency. Roosevelt took the oath of office on September 14 in the Ansley Wilcox House in Buffalo, New York. One of his first notable acts as President was to deliver a 20,000-word address to the House of Representatives on December 3, 1901 <1>, asking Congress to curb the power of trusts "within reasonable limits." For this and subsequent actions he has been called a "trust-buster."
http://en.wikipedia.org/wiki/Theodore_Roosevelt#Presidency