The first episode of The Falcon And The Winter Soldier set up the primary conflict of the series - who will be Captain America? Will it be Sam Wilson, the Falcon, as Steve Rogers intended? Or will it be John Walker, the government-sanctioned replacement for Captain America? In the comics, there have been many to hold the mantle of Captain America.
Some of them have been Captain America in the main continuity of the main Marvel Universe, or Earth-616. Others have been Captain America in alternate realities or timelines. All of them have been equally important to the legacy of the iconic Marvel Comics character.
Ultimate Captain America
The Ultimate Comics line from Marvel that began in the early 2000s is likely best known for the introduction of Miles Morales as Spider-Man (who is about to become Falcon in the upcoming Heroes Reborn comic event). But Earth-1610 introduced new versions of all Marvel's classic heroes, including Captain America.
This version of the character was much more militant and prone to violence. He also has superhuman strength and durability as a result of the super-soldier serum, as opposed to the merely enhanced strength and stamina the classic character does.
Soldier Supreme
Soldier Supreme is an amalgamation of Captain America and Doctor Strange, a creation of a reality-warping event in the comic book storyline Infinity Wars. In the comic, Gamora altered reality with the Infinity Gems, smashing many heroes together into one.
Soldier Supreme was created by a magical super-soldier serum from the Ancient One, and he became a hero who fought for truth and justice alongside his sidekick Bucky Wong, a portmanteau of the comic book Bucky Barnes and Dr. Strange's partner Wong.
Danielle Cage
Danielle Cage is the Captain America of an alternate future and is the daughter of Jessica Jones and Luke Cage, who fans might be familiar with from the Netflix Marvel shows. She's also named after Danny Rand, the Iron Fist.
Danielle is Cap in the Ultron Forever dystopian reality, where she's mentored by a version of Black Widow. She eventually fights alongside the Earth-616 Avengers but goes back to her own reality, where she heads up the U.S. Avengers.
Earth X
Another dystopian version of the Marvel Universe appeared in Earth X. This 1999 limited series featured painted covers by famed illustrator Alex Ross and was based on an idea Ross had. The version of Captain America in this reality struggled in a reality in which everyone on Earth had gained superpowers.
This older, weary Cap kills the Red Skull, and then in later iterations of the story, dies saving the life of Mar-Vell, the original Captain Marvel. He is then later resurrected, with blue skin and an angelic appearance.
Isiah Bradley
Isiah Bradley is the focus of a 2003 mini-series Truth: Red, White & Black that exposes a dark chapter of World War II Marvel history. Bradley is one of many African-American test subjects to try and replicate the super-soldier serum of Project: Rebirth. Bradley gains the powers and abilities of Steve Rogers, but at a great cost.
He is captured by the Germans and experimented on during the war, and later suffers physically and mentally from the effects of the serum. The first episode of The Falcon And The Winter Solider actually contains a brief reference to Isiah Bradley.
Peggy Carter
A version of Peggy Carter is set to become Captain Britain in the upcoming What If..? animated series on Disney+, but she was actually Captain America in the comics. This version of the character appeared in the comic book series Exiles, about a team of heroes who hop between dimensions and realities.
In the reality of this Peggy, both Steve Rogers and Dr. Erskine are killed, and it's down to Peggy to take the experimental super-soldier serum.
Bucky Barnes
In the MCU, it doesn't appear that Bucky Barnes is worthy of the shield of Captain America, but in the comics it was different. Bucky became Captain America not too long after his shocking return in the early 2000s. Rehabilitated from being the Winter Soldier, he takes over for Steve Rogers after Steve's assassination in the aftermath of the Civil War event.
Bucky serves in the role through the Secret Invasion storyline in the comics, before eventually yielding the shield back when Steve returned a few years later.
John Walker
The man introduced at the end of the first episode of The Falcon And The Winter Soldier is John Walker, better known to comic book fans as the U.S. Agent. Walker initially appeared as a villain of sorts of Captain America in the '80s but was then chosen to take Rogers' place when he walked away from the job.
Walker was a violent, extreme person who didn't embody the ideal of Captain America Rogers did, and the two eventually clashed. Rogers took the mantle back and Walker reformed as the U.S. Agent. He also served as a member of the West Coast Avengers.
Steve Rogers
Steve Rogers is the quintessential Captain America. He embodies all of the patriotic values of his era, but also timeless beliefs in truth and freedom as well. Rogers first appeared in Captain America Comics #1 in 1941.
He was co-created by the legendary comic book team of Joe Simon and Jack Kirby. Rogers pre-dates the Marvel Comics Universe by decades, and his arrival from World War II into the early '60s was retconned with him being frozen in ice for that time.
Sam Wilson
Sam Wilson so far has turned down the shield in the MCU, but in the comics, he was less reluctant. Sam has actually taken on the mantle of Captain America on a couple of occasions. He first takes on the role in the late '90s, in the Captain America: Sentinel Of Liberty series, after it appears Steve Rogers dies.
He does so again in the 2010s. After Rogers loses the super-soldier serum and becomes an old man, he anoints Wilson as the next Captain America. Sam serves in the role for years, through the All-New, All-Different era of Marvel.