Captain America was first conceptualised by Joe Simon in 1940. He was named as the Super American at first, before Simon decided that there were too many "Supers" around and went with Captain instead.

Cap's sidekick was named simply as Bucky, after the creator's buddy Bucky Pierson.

As for the visual, the great Jack Kirby inked it.

Cap first appeared in Captain America Comics #1 (cover dated March 1941) from Timely Comics, a predecessor of Marvel Comics, and it sold almost 1 million copies. He was also the first Marvel Comics character to have appeared in media outside comics with the release of the 1944 movie.

With that, the first fan club was formed for the followers of the superhero and it was named the "Sentinels of Liberty".

Notably, in 1948, Bucky was shot and Cap's girlfriend Betsy Ross replaced the young fella as Cap's newest sidekick and named herself the Golden Girl. Not Agent Carter at that point of time.... But the non American may not be so familiar with that name. Betsy Ross, full name Elizabeth Griscom Ross, was better & widely known as the lady who sewn the first American flag.

Stan Lee joined the creative team during issue 3, while the dynamic duo who created the character left for DC Comics after issue 10.

Although primarily designed with a patriotic personality, after fighting Nazis and Japanese during the World War II era, Captain America retained his patriotism for his country and has evolved to more of a fight for the common mankind.

In his career of fighting the baddies, Cap was not always a winner. After the war, the title had its downfall in sales circulation and several revival attempts by different publications.

It was not till an villian imposter did a test-water appearance in Strange Tales #114 for the character, reviving the reaser's interest in the character, which led to the subsequent "first silver age appearance" for Cap in Avengers #4.

That credit, would definitely goes to Stan Lee, Jack Kirby, and nonetheless the main star for that issue of Strange Tales - Johnny Storm.

At this point of time, the story got rebooted to the storyline where most of you are familiar with from the movie of the "Captain America : The First Avenger".

As all of us would get lethergy from our jobs, so does the Cap. Since his career reboot in the silver age of 1964, we saw the ups and downs in the star-spangled hero when he quitted and picked himself up again, ran for the presidency, the few flings he had, and of course the eventual "death".

We shall end off his character intro with the few who had donned the uniform:

 

Steven Rogers (aka Steve Rogers)

Born in the 1920s in the Lower East Side of Manhattan, New York City, to poor Irish immigrants, Sarah and Joseph Rogers. Joseph died when Steve was a child, and Sarah died of pneumonia while Steve was a teen. By early 1940, before America's entry into World War II, Rogers is a tall, scrawny fine arts student specializing in illustration, and a comic book writer and artist.

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William Naslund (aka Spirit of '76)

Born in Philadelphia, Pennsylvania. An athletic young man, hoping to help the Allies' World War II efforts in a unique way, he develops exceptional fighting skills and learns to copy some of the moves Captain America employed with the discus-like shield that he carried. He is recruited by a mysterious man called "Alfie" to become a costumed hero in the new team of adventurers called the Crusaders, till he discovered that Alfie was actually a German agent.

When Cap & Bucky went missing in 1945, U.S. President Harry Truman recruited Naslund and a young man named Fred Davis to become the new Captain America and Bucky.

Jeffrey Solomon "Jeff" Mace/ Jeffrey Mace (aka The Patriot)

Born in Brooklyn, New York. He was a reporter at the Daily Bugle, who was inspired to become a superhero after seeing Captain America in action.

As the Patriot, Mace becomes one of several superheroes who fight Nazi saboteurs and supervillains during World War II.

After the death of Naslund in a skirmish, Mace is recruited to be the third Captain America, retiring in 1949. He marries Betsy Ross, who eventually died of cancer in old age and modern timeline.

William Burnside (aka The Grand Director)

He was a history graduate enamored with the Captain America mythos, having his appearance surgically altered to resemble Rogers and legally changing his name to "Steve Rogers", becoming the new "1950s Captain America".

Burnside actually attained a PhD during the 50s, and he has actual superhuman strength. His agility, dexterity, speed, reflexes, coordination, balance, and endurance are superior to those of any Olympic athlete, and his physiological functions operate at the peak of human efficiency. He is a trained boxer and a competent hand-to-hand combatant.

John Walker (aka Super-Patriot, U.S. Agent)

Walker was born in the fictional town of Custer's Grove, Georgia. He grew up idolizing his older brother, Mike, a helicopter pilot who died in the Vietnam War. John wanted to honor his brother's memory by enlisting in the military, becoming a soldier himself.

After John received an honorable discharge from the United States Army, he was told by a friend about the Power Broker, a mysterious individual who gave people superhuman abilities. Walker and his friend received treatments that granted him superhuman abilities.

Walker was ordered to take up the role when the original Captain America, Steve Rogers, abandons his costume and identity.

James Buchanan "Bucky" Barnes (aka Bucky, Winter Soldier)

Bucky was born in Shelbyville, Indiana in 1925. He is an orphan, the son of a soldier killed in training at U.S. Army Camp Lehigh in Virginia just before the United States' entry into World War II. As a result, he is unofficially adopted by the camp as a mascot. Nicknamed "Bucky", he takes to wearing a uniform and becoming savvy with the ins and outs of military life, even though he is a teenager. It was at Lehigh that he meets and befriends Private Steven Rogers, who by all appearances is the clumsiest soldier in the camp.

In 1940, Bucky accidentally walked in on Steve Rogers changing into his uniform, thus discovering his friend was Captain America and insisted that he join him. He underwent extensive training and was assigned to be Captain America's partner. The military justified putting a 15-year-old in harm's way by using him as a symbol to rally the youth of America.

After the "death" of Steve Rogers, Tony Stark receives a letter containing Rogers' request that Bucky become the next Captain America, which Bucky agrees.

Adopting the original shield, he dons a new costume incorporating a pistol and a knife.

Samuel Thomas Wilson (aka Sam Wilson, The Falcon)

Born in Harlem, New York City, to Paul Wilson, a prominent minister, and Darlene Wilson. Wilson has a happy childhood and finds he has a natural affinity for birds. He takes up training pigeons, and has the largest pigeon coop in Harlem. In his teens, however, encounters with racism leave him jaded. When he is 16, Wilson refuses to join the church, believing his deeply religious parents to be ignorant for their faith. To his surprise, rather than put up a fight, his parents provide him with books on different religions and comparative theology. The next night, however, Sam's father is killed trying to break up a neighborhood fight.

Two years later, his mother is shot and killed by a mugger one block from their apartment. Consumed by grief and "angry at the world" Sam turns his back on his past as a respected community volunteer. He moves to Los Angeles and creates a new persona: "Snap" Wilson, a professional criminal and gang member.

While Snap is on his way to "a big score in Rio de Janeiro", his plane crashes on Exile Island, where he later finds and befriends Redwing, a falcon with which he feels a remarkably strong bond.

Wilson has shown some ability to apparently control birds. He was proven by Charles Xavier to be having telephatic link with Redwing and other birds.

When Steve Rogers decided to take on a role as mission coordinator, organizing the Avengers' plans of attack, he appointed Sam Wilson as his official "replacement" as Captain America.

The Many Faces of Captain America

The above introductions to the characters were mainly extracted from wikipedia, but simplified and summarised for easier reading.

However, to be honest, the role and power that followed being the Captain America are so strong, the list could grow longer if we really continue digging and pursuing. So many alternate dimensions and earths and variants we have yet to explore.

But nevertheless, about the mainstream storyline, that should be it.

Should we have more time in the future, we may as well list out the love interests of the great White, Blue and Red.