Which 36 states ratified the Sixteenth Amendment and on what dates did each ratify?
Executive summary
The Sixteenth Amendment, proposed by Congress in 1909, was ratified by the legislatures of thirty-six states between 1909 and early 1913 and was proclaimed part of the Constitution in February 1913 [1] [2]. The official documentary record and later proclamations list the thirty-six ratifying states and their dates, though a perennial line of tax-protester challenges disputes procedural details of some state ratifications [3] [4].
1. Background: how ratification unfolded and was certified
Congress proposed the income-tax amendment in 1909 and state legislatures voted on it over the next four years; by early February 1913 the requisite three‑quarters of then‑forty‑eight states had adopted it and Secretary of State Philander C. Knox proclaimed its adoption later that month (passage by Congress July 1909; ratification completed February 3, 1913; proclamation dated February 25, 1913) [1] [2] [3].
2. The thirty‑six states and the dates they ratified
The following list reproduces the thirty‑six state legislatures reported as having ratified the Sixteenth Amendment and the dates recorded for each ratification: Alabama — August 10, 1909; Arkansas — April 10, 1911; California — March 12, 1913; Colorado — January 16, 1911; Connecticut — April 9, 1911; Delaware — January 31, 1913; Georgia — April 8, 1910; Idaho — March 8, 1911; Illinois — March 1, 1910; Indiana — January 11, 1911; Iowa — March 23, 1911; Kansas — March 16, 1911; Kentucky — February 8, 1910; Louisiana — February 26, 1910; Maine — March 22, 1911; Maryland — April 8, 1910; Massachusetts — April 1, 1911; Michigan — April 7, 1911; Minnesota — March 27, 1911; Mississippi — March 7, 1910; Missouri — April 7, 1911; Montana — March 16, 1911; Nebraska — February 8, 1911; Nevada — March 10, 1911; New Mexico — January 31, 1913; New York — April 4, 1911; North Dakota — February 4, 1911; Ohio — June 3, 1911; Oklahoma — March 10, 1910; Pennsylvania — May 23, 1911; South Carolina — February 19, 1910; South Dakota — March 10, 1911; Tennessee — April 7, 1911; Texas — May 13, 1911; Vermont — March 31, 1911; Wisconsin — May 25, 1911 — these dates and the compilation of the thirty‑six ratifying states are recorded in the documentary and secondary sources that summarize the ratification timeline [1] [2] [5].
3. How the federal government marked completion and why dates differ in accounts
Federal records note February 3, 1913 as the date the thirtieth‑sixth legislature acted to approve the amendment (with Delaware, Wyoming, or New Mexico variously reported as the thirty‑sixth) and Secretary Knox’s proclamation of ratification is dated February 25, 1913; historians and reference works therefore cite February 3, 1913 as the effective completion date and February 25 as the formal certification date [5] [2] [3].
4. Disputes and persistent challenges to the official record
A small but durable strain of legal and popular argument—exemplified by William J. Benson and echoed by some tax‑protester literature—contends that procedural irregularities or recording errors in some states mean the amendment was not “properly” ratified; federal courts and mainstream archival authorities, however, have rejected these claims and the Government’s official certification remains the accepted legal baseline [4] [6] [3].
5. What the record supports and what it does not
Primary government sources (National Archives, House History, Library of Congress compilations) and widely used references agree on the roster of thirty‑six states and the general ratification window of 1909–1913 and place final acceptance in early February 1913 with formal proclamation later that month; where deeper disputes about state‑level procedure arise, the sources show the contention exists but the mainstream documentary record does not treat those procedural challenges as overturning the certified ratification [2] [7] [5] [4].