How Did Old Captain America Return To The Main MCU Timeline?

Marvel's Avengers: Endgame left one last Captain America mystery unsolved: How did old Steve Rogers return to the original Marvel Cinematic Universe timeline? The Avengers: Endgame ending saw Steve Rogers use Pym particles to venture through the Quantum realm and travel through time in order to return all the Infinity Stones to their original place in the timeline. Then, instead of returning to the present, he chose to stay in the past and spend his life with Peggy Carter.

The final shot of Avengers: Endgame is Steve finally getting his dance with Peggy that he promised her all the way back in Captain America: The First Avenger. It's meant to symbolize Steve finally being done sacrificing for the greater good and acting selfishly just for once—the inverse of Tony Stark's ending as Iron Man, which saw the selfish genius billionaire playboy sacrifice his life to defeat Thanos. However, the film's ending leaves one mystery unsolved, in that it never explains how Steve returned to the present MCU timeline.

Endgame's Ending Doesn't Answer How Old Captain America Returns

Instead of returning on the platform the Avengers use for time traveling, old Captain America appears a few moments later sitting on a bench by the nearby lake. However, it's never revealed how Steve made his way to the bench. He doesn't return to the time travel platform, which is the only one of its kind in existence, since it was rebuilt after Thanos destroyed the Avengers' compound in his attack.

The conversation between Steve Rogers and Sam Wilson when old Captain America does return is focused mostly on the shield and the superhero mantle. Though Steve does mention his decision to get a life, he doesn't reveal how exactly he made that happen or how he returned to the present. Then, the conversation quickly shifts to Steve passing on the Captain America shield to Sam, before the movie cuts to Steve's dance with Peggy.

The Russos Explained Steve Rogers' Reappearance In Endgame

In terms of knowing how old Captain America may have returned from the past, it's important to understand exactly where he was and, unfortunately, those involved in telling Steve Rogers' story don't all agree. Avengers: Endgame directors Joe and Anthony Russo have said they believe Steve created a branch timeline when he stayed in the past. If that's true, it means that if Steve had wanted to travel back to the main MCU timeline, he'd have to travel between timelines, not just backward or forward in the main timeline. But it's unclear if the Pym suits and particles were capable of traveling from a branched timeline to the main timeline.

Another wrinkle in that explanation is the MCU Phase 4's introduction of the Time Variance Authority. If Steve had created a branched timeline, surely the TVA would have intervened and either gotten rid of him or put him back in his original time. So, if Steve was living in a branched timeline, Marvel needs to explain how he would've traveled from that timeline to the prime MCU timeline, and why that branched timeline was allowed to exist.

However, the Russos' idea of what happened to Steve is different to what the writers, Christopher Markus and Stephen McFeely, think. They claim that Steve stayed in the main MCU timeline and staying in the past didn't create any branched timelines because he was always meant to be there. This explanation solves the problem of the branched reality and does offer a possible way old Captain America appeared at the end of Avengers: Endgame.

Endgame's Ending Still Has A Major Unanswered Mystery

If the Russos are right and Steve created a branched timeline wherein he lived out his life with Peggy separate from the main MCU timeline, he'd need a way to get back. Since it's a different timeline, one that doesn't have Captain America as part of the Avengers, it stands to reason they may never have developed the tech he'd need to get home. Or, if they did, it could have been different in a way that made it impossible for him to return. But, if Steve could still use the suit and Pym particles he used to put the Infinity Stones back, it's unclear how he could've returned without the platform since there may not be one in the branched timeline and there was only one in the prime timeline.

It makes much more sense for the Russos to be wrong about Steve creating a branched reality and instead staying in the MCU timeline. That way, he could simply wait, without needing to time travel or travel between timelines. Of course, then he'd need to sneak over to the bench while Sam, Bucky and the Hulk's backs were turned, but that seems more doable than the other options.

Still, this is all speculation based on what's in the movie and the creatives' conflicting statements about what they think happened to Steve. The MCU has yet to explain in canon how old Captain America returned to the main MCU timeline to give the shield to Sam. Whether it happens in Captain America: Brave New World, Thunderbolts, Avengers: The Kang Dynasty or Avengers: Secret Wars, Marvel needs to solve this one last Avengers: Endgame mystery and clear up all the confusion surrounding how old Captain America returns.