Wikipedia:
On February 3, 1959, a small-plane crash near Clear Lake, Iowa, killed three American rock and roll pioneers: Buddy Holly, Ritchie Valens, and J. P. “The Big Bopper” Richardson, as well as the pilot, Roger Peterson. The day was later called The Day the Music Died by Don McLean, in his song “American Pie”. The plane crash has been called the first and greatest tragedy rock and roll has ever suffered.
There would be others, but this was the first.
For my money, J.P. Richardson, aka “The Big Bopper”, while by all accounts an amiable fellow, was something of a novelty act. Ritchie Valens, of course, was an important figure in early rock ‘n roll, and without question, the importance of Buddy Holly simply cannot be overstated.