S.J. Res. 40, Joint Resolution proposing an amendment to the Constitution of the United States, June 28, 1909
A Senate resolution to amend the Constitution passed both houses of Congress in July 1909. It proposed empowering Congress to levy income taxes directly on the people. On February 3, 1913, Delaware became the thirty-sixth state to ratify, fulfilling the three-fourths majority requirement. Secretary of State Philander Knox certified the ratification of the Sixteenth Amendment on February 25.
Records of the U.S. Senate, National Archives and Records Administration
The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration
A National Income Tax
In 1872 Congress repealed a national income tax that had helped finance the Civil War, but the question of whether to tax income reemerged after a financial panic in 1893 heightened the need for federal revenue. Representative William Jennings Bryan of Nebraska, along with farmers, populists, and progressives, advocated a graduated income tax. When an income tax bill passed Congress in 1894, however, the U.S. Supreme Court declared it unconstitutional. Congress finally secured its power to tax income in 1913 after it approved, and the states ratified, the Sixteenth Amendment.
But gentlemen have denounced the income tax as class legislation. . . . why should not those sections pay most which enjoy most?
Representative Williams Jennings Bryan of Nebraska, Speech to the U.S. House of Representatives, January 30, 1894