Warning: Contains SPOILERS for What If...? episode 1.

Thanks to Marvel's What If...?, the MCU has confirmed exactly when Steve Rogers became Captain America. The so-called "Living Legend of World War II," Steve Rogers was the first super-soldier created by the United States. He soon donned a patriotic uniform to become Captain America, leading the Allies in the fight against Hydra.

Captain America is not the only super-soldier in the MCU, but he is undoubtedly the greatest. But, as famous as his story may be, his origin story Captain America: The First Avenger was actually wary of pinning down the date he was transformed. Marvel only confirmed a specific date in an Instagram post back in 2016, revealing Project Rebirth took place on June 22, 1943. Given this was never officially stated in-universe, though, the canonicity of this has naturally been open to debate.

Related: Red Skull's Tesseract Monster Explained: Marvel Comics History & MCU Future

Marvel's What If...? episode 1 has officially confirmed the date of Abraham Erskine's Project Rebirth experiment. Although this is set in a different timeline, according to the "Voice of God" character the Watcher it diverged when Peggy Carter decided to remain in the Rebirth chamber rather than watch Steve Rogers' transformation from a viewing booth; thus every detail up to that point corresponded with the main timeline. And the Watcher specifically states this moment in MCU history took place in June 1943. It looks as though that Instagram post has been embraced by the MCU's wider canon.

skinny Steve Rogers Captain America First Avenger

Marvel's What If...? explores diverse timelines, introducing viewers to worlds in which Peggy Carter became a super-soldier instead of Steve Rogers, T'Challa was kidnapped by Yondu as a child rather than Peter Quill, and Doctor Strange turned evil due to a personal tragedy. But, because each of these alternate dimensions branches out from the main MCU timeline, the show also offers a unique window into the history of the Marvel Cinematic Universe. In this case, it has confirmed the precise date Steve Rogers was subjected to the super-soldier serum, and in doing so it has verified that statements on official promotional accounts do matter in the MCU.

The question of canonicity has always been something of a "hot topic" for the MCU, particularly as regards whether or not Marvel tie-ins should be considered canon. Speaking on Twitter, James Gunn declared a prelude comic for Guardians of the Galaxy non-canon when he wrote the sequel, because he wanted to write a different origin story for Gamora. And Black Widow contradicted the Avengers: Infinity War Prelude when it retconned Steve Rogers' jailbreak from Captain America: Civil War. A show like Marvel's What If...?, that bounces around the timeline, always had the potential to cause continuity problems - but it seems its writers have taken great care not to do so, and in this case they've confirmed an Instagram post is canon when it was previously up for debate.

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Marvel's What If...? releases new episodes Wednesdays on Disney+.

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