Akhil Reed Amar, in this installment of his Yale course on the Constitution, traces the amendments of the Progressive Era. He argues the federal income tax was constitutional even before 1913, noting that Lincoln signed one during the Civil War and that the Supreme Court's later reversal, over Justice Harlan's dissent, rested on a reading of 'direct tax' tied to slavery-era compromises. He walks through the Seventeenth Amendment's prehistory, from the Lincoln-Douglas contest through southern primaries and Oregon's pledge system, and its effects on cabinet service and the path to the presidency. The fullest section covers the Nineteenth Amendment: why western territories with far more men than women enfranchised women first, how state votes swung from lopsided losses to a bandwagon, and why Woodrow Wilson reversed course and asked Congress for suffrage as a war measure.