IIRC, that had to do with federal highway funds. The feds were pushing for a uniform nationwide drinking age of 21, and threatened to withhold the money from states that didn't comply. I got screwed three times on that deal. I was born in Feb of 62', right before I turned 18, Mass bumped the drinking age to 19 in Jan of 80'. Then in Jan of 81', Mass bumped it up again to 20. But in Sept of 81', I went to tech school in Ohio, which had already made their drinking age 21. So I never got to drink legally anywhere until was 21.