The 16th Amendment has three dates worth knowing. Congress passed the resolution proposing it on July 2, 1909. The states completed ratification on February 3, 1913. Secretary of State Philander C. Knox certified it as part of the Constitution on February 25, 1913. Those are the 16th Amendment dates that gave the federal government explicit authority to tax income without dividing the burden among states by population.1National Archives. 16th Amendment to the U.S. Constitution: Federal Income Tax
Why These Dates Mattered
Before 1913, the federal government funded itself mainly through tariffs and excise taxes. A Civil War income tax had come and gone by 1872, and when Congress tried again in 1894, the Supreme Court struck the law down. In Pollock v. Farmers’ Loan & Trust Co., decided April 8, 1895, the Court held that a tax on income from property was a direct tax that had to be apportioned among the states by population, as the original Constitution required.2Justia. Pollock v. Farmers’ Loan and Trust Co.
Apportionment made a national income tax essentially unworkable. A state with 10 percent of the population would owe 10 percent of the total, regardless of what its residents actually earned. The only way past Pollock was to amend the Constitution.
July 2, 1909: Congress Passes the Resolution
The 61st Congress passed Senate Joint Resolution 40 on July 2, 1909.1National Archives. 16th Amendment to the U.S. Constitution: Federal Income Tax The House approved it 318 to 14, with 55 members not voting.3History, Art and Archives, U.S. House of Representatives. The Ratification of the Sixteenth Amendment The Senate passed it unanimously. Support was lopsided because many lawmakers were frustrated with the tariff system, which they saw as loading costs onto consumers while leaving wealthy investors untouched.
Constitutional amendments don’t require a presidential signature. Once both chambers approved the resolution, it went to the state legislatures. The proposed amendment was formally transmitted to the states on July 16, 1909.4GovInfo. Constitution of the United States – Amendment XVI Its text was a single sentence: “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.”5Congress.gov. U.S. Constitution – Sixteenth Amendment
August 10, 1909 to February 3, 1913: State Ratification
Alabama moved first, ratifying on August 10, 1909, barely a month after Congress proposed the amendment.6Constitution Annotated. Early Twentieth Century Amendments Over the next three and a half years, state legislatures debated the measure during their regular sessions. Momentum built in part on the argument that a federal income tax would let Congress lower tariffs and reduce the price of everyday goods.
Ratification was completed on February 3, 1913, when the thirty-sixth state approved the amendment. Delaware, Wyoming, and New Mexico all ratified that same day, and it remains unclear which legislature technically cast the decisive vote. The Union then had 48 states, so 36 met the three-fourths threshold. Additional states ratified afterward. Only Connecticut, Rhode Island, and Utah formally rejected the amendment and never reversed those votes.6Constitution Annotated. Early Twentieth Century Amendments
February 25, 1913: Secretary Knox Certifies the Amendment
Secretary of State Philander C. Knox issued the official proclamation certifying the 16th Amendment on February 25, 1913.1National Archives. 16th Amendment to the U.S. Constitution: Federal Income Tax The proclamation confirmed that the required number of states had approved the change and that it was now part of the Constitution. From that date, the federal government had unambiguous authority to tax income without apportioning the burden by state population.
Certification ended nearly two decades of legal uncertainty left by Pollock. Congress no longer had to build tax bills around apportionment, which had made any practical income tax impossible. Knox’s proclamation is the reason February 25, 1913, rather than the February 3 ratification date, is sometimes cited as the date the amendment “took effect.”1National Archives. 16th Amendment to the U.S. Constitution: Federal Income Tax
October 3, 1913: The First Income Tax Under the Amendment
Congress moved quickly after certification. President Woodrow Wilson signed the Revenue Act of 1913, also called the Underwood-Simmons Act, into law on October 3, 1913. It imposed a 1 percent tax on net personal income above $3,000 and added a graduated surtax reaching 6 percent on incomes over $500,000.7Internal Revenue Service. Historical Highlights of the IRS The thresholds were high enough that fewer than 1 percent of the population owed anything.1National Archives. 16th Amendment to the U.S. Constitution: Federal Income Tax
The law introduced Form 1040, still the standard individual return more than a century later.7Internal Revenue Service. Historical Highlights of the IRS The act made tax obligations retroactive to the date of certification earlier that year, capturing income earned during most of 1913. What started as a single-sentence amendment traces back to those three dates in 1909 and 1913 when Congress, the states, and a Secretary of State each played a part in changing the Constitution.