Starting with the 16th Amendment passed in 1913, a total of 12 constitutional amendments were ratified in the 20th century. In no other century were so many amendments passed. The first 11 amendments were added to the U.S. Constitution in its earliest years, between 1791 and 1795. After that, only four more were added in the 19th century. The 27th Amendment is the most recent amendment added to the U.S. Constitution. It was ratified in 1992.

Congressional Amendments

The first and last of the 20th century amendments regard the powers of Congress. The 16th Amendment modifies Article I, Section 9 of the Constitution, and gives Congress the right to levy an income tax upon U.S. citizens. The 27th Amendment prohibits Congress from allotting itself pay raises during a current session. It mandates that pay raises must take effect in a subsequent session, so that citizens may vote for their representatives in the interim. Although this amendment was originally introduced in 1789, it did not become ratified for more than 200 years.

The Right to Vote

Five of the 20th century amendments regard the right to vote. The 17th Amendment gives citizens the right to vote directly for their senators. Before this amendment was passed in 1913, senators were selected by state legislatures. The 19th Amendment, passed in 1920, granted women the right to vote. In 1961 the 23rd Amendment granted the citizens of Washington D.C. the right to vote in presidential elections. The 24th Amendment, passed in 1964, bans the implementation of a poll tax and ensures that all citizens will be able to vote regardless of their financial status. Lastly, in 1971 the 26th Amendment lowered the legal voting age from 21 to 18. It was passed in the midst of the Vietnam War, when the slogan "Old Enough to Fight; Old Enough to Vote," accurately depicted the public opinion. This amendment was ratified faster than any other amendment in U.S. history.

Prohibition

The 18th Amendment, passed in 1919, began the era known as Prohibition. This amendment prohibited the sale of any alcoholic beverage on United States soil. Prohibition was intended to protect citizens from the effects of alcohol abuse. However, it is generally regarded to have had the opposite effect by glamorizing the consumption of liquor and also providing a means to fund new organized crime syndicates. The sale of alcohol continued to be outlawed until 1933, when the 21st Amendment repealed the 18th.

Presidential Amendments

The three remaining amendments of the 20th century all center on the office of the presidency. In early 1933, the nation was in the midst of the Great Depression and needed decisive action from their new president, Franklin Delano Roosevelt. However, he wasn't able to take office until March. For this reason, the 20th Amendment was passed, moving the date of the presidential inauguration to January 20. The 22nd Amendment is also closely tied to FDR's presidency. He was the only president to serve more than two terms, which had previously been tradition though not mandated by law. When Republicans regained control of Congress in 1951, they quickly set about passing the 22nd Amendment to ensure the two-term tradition was mandated in the Constitution. Lastly, the 25th Amendment codifies the rules for presidential succession in the event of a president's death or removal from office.