Three decades later, thanks to the entire Beatles catalogue now being on iTunes, a whole new generation is embracing the genius of Lennon -- all that he gave us, and all the potential of a life that ended much too soon.
There will be vigils worldwide tonight, including ones in New York and in Lennon's hometown of Liverpool, England.
"The Early Show" asked Chris Carter, who hosts "Breakfast with the Beatles," a popular weekly radio program, for some reflections.
Carter said, "What we lost was the greatest songwriter of our generation. John Lennon affected more people in a short period of time than anybody else I can think of. His loss, I think, overall, it shook every member, not only of the entertainment business, but pop culture, society, everybody in America."
"This was just like boom, out of nowhere," Carter says of Lennon's death. "And that's why so many people you know went to the Dakota and just grieved together. It was just this incredible sea of fans young and old."
Carter said he thinks about how Lennon would be today.
"There's so many things we never got to hear from John," Carter said. "The possibilities were endless, you know those were all taken from us. And I think the loss, you know, we'll never be able to -- I don't think we can ever get that back, that feeling that you got from listening to John's music."
Lennon's music lives on -- and then some. Just a week after the Beatles catalogue went up on iTunes, fans purchased 500,000 albums, and downloaded two million individual tracks. The image you have of John Lennon may be one frozen in time. He would have turned 70 this year.
Mark David Chapman, the man who pulled the trigger, is now serving a life sentence. Chapman had gotten Lennon's autograph the day he was shot. Chapman has actually been up for parole six times and denied six times. Lennon's widow, Yoko Ono, has testified at those parole hearings.