The founders built a structural limit on federal taxing power, a restriction the Progressive Era removed. The government that followed was not a coincidence.

The 16th Amendment, ratified Feb. 3, 1913, gave Congress the power to tax income “from whatever source derived, without apportionment among the several states.” Those 23 words eliminated the constitutional constraint that Pollock v. Farmers’ Loan and Trust Co. (1895) had enforced: an income tax on investment income was a direct tax requiring apportionment by population, a structural protection the founders had written into the original Constitution with specific intent.