ON SEPTEMBER 6, 1901, President William McKinley was shot by Leon Czolgosz, an anarchist, while attending the Pan-American Exposition in Buffalo, New York. Eight days later, McKinley died, and Theodore Roosevelt became president. Roosevelt immediately reassured the shocked nation that he intended “to continue absolutely unbroken” the policies of McKinley. But Roosevelt was quite different from McKinley. An activist and a moralist, imbued with the progressive spirit, Roosevelt would turn the White House into a “bully pulpit,” advocating conservation and antitrust reforms and championing the nation’s emergence as a world power. In the process, Roosevelt would work to shift the nation’s center of power from Wall Street to Washington.

After serving nearly two full terms as president, Roosevelt left office at the height of his powers. Any man would have found it difficult to follow in his footsteps, but his handpicked successor, William Howard Taft, proved hopelessly ill suited to the task. Taft’s presidency was marked by a progressive stalemate, a bitter break with Roosevelt, and a schism in the Republican Party.