system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How and why was it decided that 18 is the age when someone becomes an adult?
gpt
The age of majority is actually very complicated and is different for different states and different things.  The age of majority in Alabama and Nebraska is 19 and in Puerto Rico and Mississippi it is 21.  A lot of other states use 18, but if someone is still in high school, they are still considered a minor.  The reason most places in the US think of the age of 18 as the age of majority is because of certain events in history.  When the draft in World War II was initiated, the age of majority in most of the US was 21.  FDR needed more soldiers, so he lowered the age for the draft to 18.  In the 1960s and 1970s, there was a movement to lower the voting age from 21 to 18 because the idea that someone could be drafted to go to war but not be allowed to vote was repugnant to many.  So, Richard Nixon lowered the voting age to 18 in the year 1970, and the US eventually passed the 26th amendment setting the voting age at 18.  Most states shortly afterwards changed their age of majority to 18, but some did not.