Once upon a time, before MTV, it was pretty common to have no idea what your favorite band looked like. This is almost incomprehensible to the younger generations who are often more familiar with a band's image than their actual music.
Think about it. A lot of bands had album artwork rather than their ugly mugs on the cover. Musicians like Kansas, Yes, Meatloaf, Boston, Chicago, and Styx adorned their records with paintings, not band photos. Also, you primarily heard the artists on the radio, not on the TV. For instance, I heard all of The Little River Band's hits and had absolutely no idea what they actually looked like.
Christopher Cross is often cited as the last of the butt ugly musicians. After him, MTV took over and it became about the image rather than simply the music. You can basically divide music up into two periods: B.C. and A.D. (Before Cross and After Duran).
With so many butt ugly bands before Christopher Cross (B.C.), who can decide who's the ugliest? Lynyrd Skynyrd were no glamour boys, to be sure. But the hillbilly look was their shtick, so that rules them out. Meatloaf wasn't exactly easy on the eyes, but just being morbidly obese doesn't make you the ugliest ever.
Quiet Riot, Queen and Twisted Sister were some ugly SOB's, but they had at least one decent looking dude in the band, so that rules them out. I've looked at some other "ugliest band" lists on the Internet, and left a bit dissatisfied - most use current photos of the musicians and that's simply not fair. I get it, Alice Cooper is insanely ugly, but he's also pushing seventy years old.
So, who tops my personal list as the ugliest band in history? Although The Association are pretty damn ugly (at top of post), I think the winner would have to be Dr. Hook & the Medicine Show. Ta-da!