55 years ago, a radio event happened. Now, you can hear it again.

Fifty-five years ago – almost 56, actually, since it first aired in February of 1969 – the station that helped change radio forever presented a special that helped change music history forever. It was February 21, 1969, at noon – the beginning of George Washington’s birthday holiday weekend – that KHJ (930 AM) presented “The History of Rock and Roll,” a 48-hour “rockumentary” that chronicled the events leading up to and through the evolution of popular music into rock and roll.

That first edition...