Many comic book historians would likely argue that the most important date in comics history is April 18, 1938, the publication date of Action Comics #1. After all, that issue introduced Superman to the world, and by extension, the entire superhero genre. But, I believe July 2, 1963 is the most important date in comic book history. On that date, Marvel Comics published X-Men #1 and Avengers #1, both by Stan Lee and Jack Kirby.

Marvel Comics

These two franchises, at different moments, change the face of not just comics culture, but pop culture in general, especially these past two decades. From a seed that was planted on drug store comic book spinner racks in 1963, at 12 cents each, these comics grew into films, merchandise, and theme park franchises. And it all started because Marvel was chasing trends and trying to replicate their own earlier success. Those seeds were planted on the same day; however, it took several decades to evolve into the mighty oak it is now. This was a tree that needed a lot of water, time, and patience to grow.

Two Super Teams Ahead of Their Time

In July 1963, as far as American culture was concerned, it was mostly still the ‘50s. The “Baby Boom” was in effect, a young President had energized the country, and Elvis movies reigned supreme. But within six months, JFK would be assassinated, and the Beatles would strike their first hit on the American charts. Everything in American culture would change almost overnight. This is the environment that both X-Men and Avengers were released into the world. They were both comics that were a little edgy for the time, certainly for kids. Yet they would be perfect for the decade of change that was coming soon. And both of them only happened because Marvel’s competitor DC Comics had a big hit on their hands.

DC Comics’ Justice League Paves the Way

DC Comics/Marvel Comics

In 1960, Marvel Comics’ biggest rival DC Comics launched Justice League of America, which grouped their most iconic heroes like Superman, Batman, and Wonder Woman together in one team book. Sales were fantastic, and Marvel Comics publisher Martin Goodman heard DC’s editor-in-chief brag about the JLA sales to him during a golf game. He subsequently told his nephew and employee Stan Lee to give him a similar superhero team. Together, Lee and artist extraordinaire Jack Kirby introduced Fantastic Four to the world and Marvel Comics as we know it today was born. It was an instant hit and game changer.

But Fantastic Four was not a real riff on the “all-star heroes” team the League was for DC. Lee and Kirby kind of went against their directive when creating them. Fantastic Four succeeded anyway, but by 1962, Goodman wanted Lee to introduce more teams to Marvel. This time they had to produce one that was more like DC’s Justice League of America, a group made up of established heroes, as originally asked—and another that was more in line with Fantastic Four. It needed to be a cross between the FF in terms of aesthetics, but mixed with the teenage soap opera of Spider-Man. The results were the Mighty Avengers and the Uncanny X-Men.

Two Super Teams of Mismatched Misfits

Marvel Comics

Despite the Avengers being more like the JLA by teaming up previously established heroes, Lee and Kirby still didn’t do a one-for-one with DC’s team. It wasn’t exactly an “all-star” team, as Spider-Man was already too high a seller to be part of the group and didn’t need a boost. Iron, Thor, and Ant-Man had features in anthology titles, but not their own comics. Hulk’s title had just been canned and he needed a home. So established heroes or not, the Avengers were already different from DC’s JLA as not having all their biggest stars on one team. This made them misfits of a sort too and that appealed to teen readers who didn’t want their parent’s superheroes.

And while X-Men might have essentially looked like an FF knock-off, with the characters all in basic matching uniforms and with similar powers, there were key differences. Lee and Kirby injected a sense of otherness into the mutant X-Men that the celebrity FF didn’t have, something future X-Men writers would run with to great success. But neither Avengers nor X-Men were instant hits. They sold well enough, Avengers a bit more so, but FF and Spider-Man ruled the sales charts. By 1969, nearly every Marvel book was outselling Avengers and X-Men. Marvel decided to cancel X-Men and keep Avengers going. X-Men spent the next five years as a reprint title only.

The X-Men Dominate Comics, While the Avengers Try to Keep Pace

Marvel Comics

Throughout the ‘70s, Avengers, under writers like Steve Englehart and others, rose to become a steady seller for Marvel, and a showcase for iconic stalwarts like Iron Man and Thor. Then in 1975, Marvel introduced the “All-New, All-Different X-Men.” With series writer Chris Claremont, Uncanny X-Men became a juggernaut, overtaking the comics industry and producing spinoff after spinoff. Marvel’s Mutants received a second volume in 1991, whose first issue sold a staggering eight million copies. This led to the greenlighting of X-Men: The Animated Series in 1992, where the characters, especially breakout star Wolverine, became household names—all nearly 30 years from the moment the first issue hit newsstands.

Movie Icons for the New Millennium

In 2000, the long-awaited X-Men live-action film launched a franchise that few believed could ever work. If the ‘90s cartoon made Wolverine an icon to ‘90s kids, then Hugh Jackman made him a global icon to their parents as well. While X-Men was achieving the pinnacle of their pop culture success, Marvel Comics started to position Avengers as a title that could finally outsell their mutant colleagues. Forty years after Martin Goodman told Stan Lee to make his own “all-star” team, New Avengers added company mascots Spider-Man and Wolverine. The Avengers franchise overtook X-Men in sales. And a newly formed Marvel Studios started to think about capitalizing on the brand’s potential. From the beginning, Marvel Studios hoped to introduce their roster of heroes to big-screen success. After all, X-Men had become a global phenomenon. Why couldn’t Avengers?

Twentieth Century Films/Marvel Studios

Of course, we all know what happened next. The MCU, anchored by the Avengers films, has grossed a staggering 29.1 billion dollars. For context, the next most successful franchise, Star Wars, is a distant second at 10 billion. In short, no other franchise is likely to topple the MCU anytime soon. So what’s the lesson here? We now live in a media landscape where things need to be instant hits. If a movie doesn’t blow up the box office on opening weekend, that marks its death. If a streaming series doesn’t click right away, it gets canceled. The same goes for comics.

But decades ago, Marvel Comics knew that both the Avengers and the X-Men were great concepts, and eventually, the world would catch up to how awesome they were. Maybe Marvel should officially declare July 2 as #AvengersXMenDay? It’s certainly a pivotal shared birthday that deserves to be celebrated.