The origins of the modern income tax in the United States can be traced to a minor provision included in a revenue bill enacted by Congress in October 1913 following the ratification of the Sixteenth Amendment of the Constitution in February 1913. Hence, we will soon “celebrate”—if that is the right term—the 100th anniversary of the Sixteenth Amendment and the federal income tax, which quickly replaced the tariff as the principal source of revenue for the national government. Many will be surprised to learn that it was the governing Republican majority that set in motion this “fiscal revolution” of the early 20th century. This is particularly ironic considering that the income tax has traditionally been unpopular among Republicans. Why were conservatives in the Republican Party unable to block these policy initiatives when introduced? After all, Republicans controlled all of our national political institutions—Congress, the Court, and the White House—and conservatives held key leadership positions within the party. Populists and agrarians had advocated similar programs for decades, only to be thwarted by a determined conservative opposition. Yet suddenly at the turn of the 20th century, the Republican Party accepted a national income tax. Why? To answer this question, I examine the historical record of the votes and debates in Congress surrounding the contentious income tax of 1894 and the historic compromise in 1909 that led to the ratification of the Sixteenth Amendment, which sanctioned a national income tax. Not only did many Republicans approve these new tax policies, the arguments they advanced in support of the income tax were commonly framed in terms of “equity,” “justice,” and “fairness.” Odd as it now sounds, the income tax was viewed by a substantial number of Republicans as the most “equitable” form of taxation. At the same time, the conservative leadership made a strategic blunder in an ill-fated attempt to block the enactment of a modest national income tax. As a result, Congress approved the constitutional amendment that became the Sixteenth Amendment, as well as the legislation that included the historic income tax of 1913.