Which alternative rock musician founded the E Street Band?

Bruce Springsteen founded and led the E Street Band.

Springsteen formed the group in the early 1970s while developing his career in New Jersey. The band became his principal backing group and was named after the Belmar, New Jersey, home of keyboardist David Sancious's mother, where rehearsals took place on E Street.

The E Street Band's classic lineup included Clarence Clemons, Danny Federici, Garry Tallent, Roy Bittan, Max Weinberg, and Steven Van Zandt, although membership changed across different periods. Their expansive live sound became central to Springsteen's concerts and recordings.

Springsteen's early albums Greetings from Asbury Park, N.J. and The Wild, the Innocent & the E Street Shuffle were made before his major breakthrough with Born to Run in 1975. The E Street Band is sometimes treated as a separate act, but it is principally known as Springsteen's backing band.