[SandRat]

There was a time when voting, marrying, or entering contracts required the age of 21.

You may serve in the military at 18, or even with parents permission at age 17, but cannot buy an alcoholic drink in a bar or restaurant until you are 21.

[EQAndyBuzz]

“You may serve in the military at 18, or even with parents permission at age 17, but cannot buy an alcoholic drink in a bar or restaurant until you are 21”

IIRC, in Texas, as long as you are with a relative who is over 21 and lives at the same address you can order a drink in a bar or restaurant..