The upheavals of the 1960’s demanded nuance and moral complexity from America — and from her superheroes as well. By adapting stories to the turbulent times, Marvel Comics brought superheroes to maturity — and rocketed American comics into their so-called Silver Age.

Superheroes, like jazz, are a consummately American creation, and their history holds a four-color funhouse mirror up to America’s own. Where jazz emerged from the African musical traditions brought to America by slaves, superheroes sprang mostly from the youthful imagination of the sons of Jewish immigrants. Impoverished and excluded, these writers and artists invented an American Dream they could believe in, promulgating a secular mythology where power comes from within, and often hides behind modest secret identities.

Superman, created by Jerry Siegel and Joe Shuster, launched the superhero craze a year before war broke out, in 1938. Brightly colored tales of unambiguous good versus unambiguous evil made their first splash during the Second World War, but they felt out of place when the troops came home. A few heroes, like Superman and Bob Kane’s Batman, soldiered on, but they no longer measured the pulse of America’s youth. By the time the sixties barreled into America’s post-War years, Superman’s squeaky-clean image and otherworldly decency felt as alien as his home planet of Krypton. Uncertain times called for uncertain measures, and a different kind of heroism.

Stan Lee and Jack Kirby felt that malaise keenly. Born Stanley Lieber and Jacob Kurtzberg, both had contributed to the success of Captain America Comics in the early forties as part of the community of second generation Jewish immigrants that sparked the first superhero craze. By 1961, Lee was unhappily churning out scripts for Westerns and romances at Atlas Comics. Kirby had suffered enough mistreatment from the industry to hold a Hulk-sized grudge. Neither had anything to lose by challenging orthodoxy.

When Atlas’s publisher, Martin Goodman, decided to launch a revamped line of superhero titles, Lee and Kirby saw an opportunity. Under the new name of Marvel Comics, their first collaboration hit the newsstands in November 1961. Fantastic Four #1 upended a number of superhero tropes. Instead of inhabiting a fictional city like Metropolis or Gotham, the Fantastic Four called New York home. The heroes lived publicly without secret identities, and — for the first two issues at least — they didn’t even wear superhero costumes. Their relations embodied archetypal American relationships — boyfriend-girlfriend, brother-sister, college buddies — and, in a startling nod to realism, the characters bickered and squabbled like an ordinary family.

Never mind that they got their powers by being exposed to cosmic rays on a space mission, or that the first issue saw them confronting a subterranean villain named Mole Man. The unprecedented realism of the Fantastic Four made the team a hit. Within a few years, a legion of other gritty heroes had rolled off Marvel’s presses and into American consciousness: Spider-Man, the X-Men, Iron Man, Thor, Daredevil, and others. Like the Fantastic Four, these heroes inhabited the same world as their readers, exhibited similar foibles, and faced many of the same struggles.

Marvel’s flawed anti-heroes spoke to sixties adolescence far better than spandex-clad perfection. Teenage sidekicks, like Batman’s Robin and Captain America’s Bucky, traditionally played second fiddle to the father-figure protagonist. But Peter Parker had to go it alone. Spider-Man’s heroics — frequently misunderstood by a mistrusting world — shared space with the troubles of a high school nerd striving to find his way without reliable authority figures. American youth was captivated.

Nor did Marvel shy away from contemporary politics. Launched in 1963, The X-Men featured a team of mutants, feared and hated for being born with superpowers. Anti-mutant discrimination echoed the Civil Rights struggle; heroes clashed not just with communists, but also with evil corporations, their own government and law enforcement agencies.

Lee and Kirby’s collaboration was among the most fruitful in the history of comics. With dazzling splash pages, vertiginous foreshortening and action spilling beyond the boundaries of the panels, Kirby made much of previous superhero art seem wooden. Lee scripted chatty banter for his characters that made them feel altogether real. “Your friendly neighborhood Spider-Man” really talked and acted as if he could be your neighbor.

Feeling his creative contributions to Marvel were neither fully respected nor acknowledged, Kirby quit the company acrimoniously in 1970. The legacy that he created at Marvel with Lee, however, ensured that superheroes remained relevant as their country changed. The Marvel revolution transformed superheroes from otherworldly paragons into all-too-human superhumans coping with an often baffling world.