<P> The Revenue Act of 1913, also known as the Tariff Act, the Underwood Tariff, the Underwood Act, the Underwood Tariff Act, or the Underwood - Simmons Act (ch. 16, 38 Stat. 114, October 3, 1913), re-imposed the federal income tax after the ratification of the Sixteenth Amendment and lowered basic tariff rates from 40% to 25%, well below the Payne - Aldrich Tariff Act of 1909 . It was signed into law by President Woodrow Wilson on October 3, 1913 and was sponsored by Alabama Representative Oscar Underwood . </P> <P> Wilson summoned a special session of the Congress in April 1913 . His immediate objective was to confront the perennial tariff question, and he brought special attention to the matter by deciding to appear in person before Congress to make his appeal . He was the first president since John Adams to do so . </P>

Which u.s. president enacted the federal income tax system