When Col. Theodore Roosevelt returned from Cuba, hero of his Rough Riders cavalry unit, Republican Party bosses in New York recognized a golden opportunity and tapped him to run for governor in 1898. There were doubts, however, about his loyalty. Roosevelt had been a New York State assemblyman in the 1880s who had built a reputation for charting his own course politically. As governor, he became an energetic reformer, passing progressive legislation and rooting out graft wherever he found it, and the bosses now badly wanted to be rid of him.

They saw another golden opportunity in 1900. There would be a vacancy on President McKinley's re-election ticket, thanks to the timely death of Vice President Hobart. Roosevelt was drafted to run, and the McKinley-Roosevelt ticket handily swept the field in November. Historically, the vice presidency was a dead-end job, a sinecure with no real power that usually marked the end of a politician's career. For Roosevelt, however, it would serve as a stepping-stone to a higher office, for barely six months into his second term, President McKinley was dead. Instead of a maverick in the governor's mansion at Albany, he now resided in the Executive Mansion at Washington--what the 42-year-old chief executive, in a symbolic break with the past, would officially rename the White House. The rest is history.

This pinback from 1900 pictures McKinley, the last 19th century president, and Roosevelt, the first 20th century president.