According to an article on NPR today, it really didn't cause the panic 75 years ago that we believe it did. That the hype was brought about to sell newspapers and discredit the radio industry (see big media's suppression of new technology.) It gave a panicky, vocal minority more of a voice than it probably had any need for.
This is probably a bit of why we have a "Tea Party" movement today.
I recommend reading the article because the numbers are fascinating. Also I'd have been PISSED if I lived in Boston that night.
And just in cause you haven't heard it, I recommend taking an hour to listen to the original broadcast.