Which amendment set the minimum voting age to 18 years?

The 26th Amendment to the United States Constitution is what established the minimum voting age as 18 years. Ratified in 1971, this amendment was largely driven by the argument that if 18-year-olds were old enough to be drafted into the military and fight in wars, they should also have the right to vote in elections. This amendment reflects a significant shift in the perception of young adults' rights and responsibilities, ensuring that they have a voice in the democratic process at an age that aligns with their ability to serve their country.

The other amendments listed do not pertain to the voting age: the 19th Amendment grants women the right to vote, the 21st Amendment repeals Prohibition, and the 23rd Amendment allows residents of Washington D.C. to vote in presidential elections. Each of these has its importance in U.S. history, but none address the issue of minimum voting age like the 26th Amendment does.