The 16th, 17th, 18th, and 19th Amendments to the U.S. Constitution were ratified in a seven-year stretch between 1913 and 1920. In order, they authorized the federal income tax, replaced state-legislature selection of U.S. senators with direct election by voters, banned the manufacture and sale of alcohol nationwide, and guaranteed women the right to vote. Together they represent one of the most concentrated bursts of constitutional change in American history.
16th Amendment: Federal Income Tax
Ratified on February 3, 1913, the 16th Amendment gave Congress the power to tax income from any source without dividing the tax among states based on population.1National Archives. 16th Amendment to the U.S. Constitution: Federal Income Tax (1913) The original Constitution required “direct taxes” to be apportioned by state population, which made a nationwide income tax nearly impossible to administer fairly.2Constitution Annotated | Library of Congress. Overview of Sixteenth Amendment, Income Tax
The amendment answered the Supreme Court’s 1895 decision in Pollock v. Farmers’ Loan & Trust Co., which struck down a federal income tax passed the year before. The Court ruled that taxing income from real estate and municipal bonds counted as a direct tax, meaning it had to be divided among the states proportionally by population.3Justia US Supreme Court. Pollock v. Farmers’ Loan and Trust Co., 157 U.S. 429 (1895) That requirement effectively killed the tax, since Congress had no practical way to apportion an income tax by headcount rather than earnings.
Before 1913, the federal government relied heavily on tariffs and excise taxes. Taxing incomes directly gave the government a far more substantial and flexible funding source, one that could scale with the economy and be adjusted based on a taxpayer’s ability to pay. Every federal income tax collected since then rests on the authority this amendment created.1National Archives. 16th Amendment to the U.S. Constitution: Federal Income Tax (1913)
17th Amendment: Direct Election of Senators
Ratified on April 8, 1913, the 17th Amendment took the power to choose U.S. senators away from state legislatures and gave it to voters.4National Archives. 17th Amendment to the U.S. Constitution: Direct Election of U.S. Senators (1913) Under the original Constitution, state legislatures picked both of a state’s senators. Reformers argued the arrangement bred corruption, with Senate seats widely seen as available through backroom deals. Deadlocked legislatures also left some seats vacant for years, stripping states of full representation in Congress.5U.S. Senate. Landmark Legislation: The Seventeenth Amendment to the Constitution
The Senate’s basic structure did not change. Each state still gets two senators serving six-year terms with one vote apiece. What changed was a single phrase: “chosen by the Legislature thereof” became “elected by the people thereof.”6Congress.gov. U.S. Constitution – Seventeenth Amendment
Filling Senate Vacancies
The amendment also set the rule for vacant Senate seats. When a vacancy occurs, the state’s governor must call a special election. If the state legislature has authorized it, the governor can appoint someone to serve temporarily until voters choose a replacement at that election.6Congress.gov. U.S. Constitution – Seventeenth Amendment Most states have passed laws giving their governors this appointment power, which is why you often see a governor naming an interim senator when a seat opens mid-term.
18th Amendment: Prohibition
Ratified on January 16, 1919, the 18th Amendment banned the production, sale, and transportation of alcohol throughout the United States and extended the ban to imports and exports.7Legal Information Institute. 18th Amendment The amendment included a one-year delay before taking effect, giving the country time to wind down the legal alcohol trade.
The prohibition movement had built for decades on the argument that alcohol drove domestic violence, poverty, and political corruption. By 1916, twenty-three states had already enacted their own laws against alcohol and saloons. The amendment nationalized what many states had already begun.
Congress spelled out enforcement through the National Prohibition Act, better known as the Volstead Act, passed on October 28, 1919. It set the legal threshold at one-half of one percent alcohol, which put most beers inside the ban.8United States Senate. The Senate Overrides the President’s Veto of the Volstead Act Bootlegging, speakeasies, and organized crime flourished through the 1920s, and public support eroded.
Repeal by the 21st Amendment
Prohibition did not last. On December 5, 1933, the 21st Amendment was ratified, making the 18th the only amendment ever fully repealed.9Congress.gov. U.S. Constitution – Twenty-First Amendment Section 2 of that amendment gave states broad authority to regulate alcohol within their own borders, including whether to allow importation and sale and how to structure distribution.10Legal Information Institute. Twenty-First Amendment: Doctrine and Practice That is why alcohol laws still vary so much from state to state.
19th Amendment: Women’s Suffrage
Ratified on August 18, 1920, and certified by the Secretary of State on August 26, 1920, the 19th Amendment prohibited the federal government and every state from denying or restricting the right to vote based on sex.11National Archives. 19th Amendment to the U.S. Constitution: Women’s Right to Vote One sentence enfranchised roughly 26 million American women.
The amendment closed a fight of more than seventy years. It was first introduced in Congress in 1878. Between then and 1920, supporters used lectures, marches, lobbying, silent vigils, and hunger strikes; activists were heckled, jailed, and sometimes attacked. By 1912, nine western states had already adopted women’s suffrage on their own, and when New York followed in 1917, the political momentum became hard to ignore. President Wilson reversed his earlier opposition and endorsed the amendment in 1918. The House passed it on May 21, 1919, and the Senate followed two weeks later.12National Archives. The 19th Amendment
Barriers That Persisted After Ratification
The amendment removed sex as a legal barrier, but it did not clear every obstacle. For decades, many women of color were kept from the polls by poll taxes, literacy tests, and other bureaucratic hurdles that targeted racial minorities regardless of gender. These tactics were especially widespread across the South and went largely unchallenged at the federal level until Congress passed the Voting Rights Act of 1965, which outlawed literacy tests and directed the Attorney General to challenge poll taxes in state and local elections.13U.S. National Archives. Voting Rights Act (1965) The 19th Amendment also includes a clause giving Congress the power to enforce it through legislation, which allows Congress to reach indirect barriers to women’s voting rights, not only outright bans based on sex.14Legal Information Institute. Federal and State Campaigns for Women’s Voting Rights