On March 23, 1971, a proposal to lower the voting age to 18 years was adopted by both houses of Congress and sent to the states for ratification. The amendment became part of the Constitution on July 1, 1971, three months and eight days after the amendment was submitted to the states for ratification, making this amendment the quickest to be ratified.

Answer this question based on the passage: when did 18 year olds get the right to vote in the us? Okie... think carefully first, then make a decision:
The relevant information is: On March 23, 1971, a proposal to lower the voting age to 18 years was adopted by both houses of Congress and sent to the states for ratification. So, the answer is March 23 , 1971.