Steve Ditko, the artist who co-created Spider-Man and Doctor Strange and was as well known for his idiosyncratic politics as his contributions to comics, died in late June at 90, New York police said Friday. Ditko was found dead in his apartment on June 29th, and is believed to have died two days prior from natural causes.

Born in 1927 in Pennsylvania, Ditko began making comics during the 1950s, beginning with small publisher Charlton Comics. But he first came to prominence as part of a group of comics creators who changed the industry in the 1960s with a succession of revolutionary characters, concepts and narrative changes created for Marvel Comics.

He first joined Marvel in 1955 when it was known as Atlas comics, where he contributed stories and art in a variety of genres for titles like “Amazing Adventures,” “Strange Worlds,” “Tales of Suspense” and “Tales to Astonish.”

Things changed in the early 60s, after Atlas changed its name to Marvel. In 1962 Stan Lee and Jack Kirby had huge success with “Fantastic Four,” an immediate hit that repopularized superhero comics after years of waning interest among readers. This was quickly followed by several other Lee and Kirby collaborations, until 1962, when Lee received permission from Marvel bigwigs to create what he described as “an ordinary teen superhero.”

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After rejecting a first attempt at this new character by Kirby, Lee turned to Ditko, giving him a basic concept and the name: Spider-Man. From there, Ditko went to work designing what would become one of the quintessential superhero costumes, the red-on-blue Spidey suit, along with Spider-Man’s web shooters and other elements associated with what is one of the most popular superheroes in history.

Spider-Man debuted in issue 15 of Marvel’s just-canceled anthology series “Amazing Fantasy,” which hit stores in the summer of 1962. Despite the title’s cancellation, sales of #15 were among the highest in Marvel’s history. The company brought Spidey back seven months later with “The Amazing Spider-Man,” which has remained continuously in publication ever since.

Spider-Man was an immediate success, spawning numerous companion comics, multiple animated series, a live-action TV series, and to-date five films. The character became one of the defining characters of the superhero comics genre, and “Spider-Man” films have collectively earned nearly $5 billion worldwide since 2002.

Ditko and Lee continued to collaborate, creating iconic Spider-Man villains like Doctor Octopus (July 1963), the Sandman (Sept. 1963), the Lizard (Nov. 1963), Electro, and the Green Goblin (July 1964), Hulk villains like The Leader, and another flagship Marvel hero, Doctor Strange (1963). His work during this period began to take on the ornate, visually striking weirdness he’s best known for, particularly in stories involving Doctor Strange, that was compared to artistic aesthetic of the emerging counterculture.

But despite their output and success, Ditko and Lee increasingly clashed over artistic decisions, what Ditko felt was a lack of proper credit and compensation, and even personal, social and even political differences. Eventually the pair were no longer on speaking terms. Ditko eventually quit Marvel in 1966.

After Marvel, Ditko went back to Charlton, which paid less but offered greater creative freedom. His work at Charlton led to other characters that proved just as long-lived, if not as famous, as his creations for Marvel. Among them were The Question and Captain Atom.

It was during this period that Ditko also increasingly expressed his politics through comics. A fervent supporter of objectivism, the conservative philosophical system devised by Ayn Rand, Ditko often had his characters express similar beliefs, most famously with his independently-owned 1967 creation Mr. A, a noir-influenced superhero espousing a black and white morality and little mercy for criminals.

While The Question and Mr. A remain obscure to most non-comics readers, the characters were given a kind of immortality by Ditko’s political opposite, British comics writer Alan Moore. Moore’s character Rorschach, from his 1987 DC Comics miniseries “Watchmen,” was intended to be an amalgam of The Question and Mr. A, as a criticism of Ditko’s politics.

Ditko briefly worked for DC Comics in 1968 before returning to Charlton, where he worked until the mid-1970s. He returned to DC briefly in the late 70s, and in 1979 went back to Marvel, working on a variety of titles through the 1980s. He continued to freelance for Marvel through the late 1990s, and even into the early 2000s contributed to publishers like Eclipse Comics and Dark Horse.

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Ditko remained largely quiet about Marvel and his feelings about the company’s success with the characters he created, speaking about it only occasionally. He said more than once that he preferred to speak through his comics, and rarely granted interviews. But one of his rare public comments on the matter came in 2012, when he said that he had received no money from the successful Spider-Man films.

“By the ’70s he was regarded as a slightly old-fashioned odd-ball; by the ’80s he was a commercial has-been, picking up wretched work-for-hire gigs,” said the New York Times about him in 2008. “Following the example of [Ayn] Rand’s John Galt, Ditko hacked out moneymaking work, saving his care for the crabbed Objectivist screeds he published with tiny presses. And boy, could Ditko hack: seeing samples of his Transformers coloring book and his Big Boy comic is like hearing Orson Welles sell frozen peas.”

Ditko was inducted into the comics industry’s Jack Kirby Hall of Fame in 1990, and into the Will Eisner Award Hall of Fame in 1994.

Ditko has no known survivors and is not known to ever have married or had children.