I thing the very first was Joe Cotton Blues Band and Fleetwood Mac in "71.
After that its kind of hard to distinguish in what order, but in the starting mid 70's - The Band, The Dead, Jefferson Airplane, Ronstadt, Eagles, Poco, Willie, Springsteen,Jerry Jeff Walker, Bonnie Raitt, Marshall Tucker, Charlie Daniels, original Skynard ....
At that time I was in So Cal and was lucky to see a number of great concerts, many in small venues.