I'll put in a plug for "Allman Brothers"...or at least Dwayne Allman. Virtually no guitar player of modern times fails to credit Dwayne Allman for giving them the slide guitar technique on electric 6-stringed instruments.
With alternate tunings and that slide...think about all who followed by using that technique. So much so that the slide enters the equation on so much music today that it has to be classed as a "staple". Clapton learned it from Dwayne as did Joe Walsh. Look at what Keith Richards has done with open tunings both with and without a slide. Nearly all of that is attributed to Dwayne Allman!
Something to think about!
As for the group, they are generally associated with the beginnings of Southern Rock as a genre. They didn't originate it necessarily, but they really gave it mass appeal.