“Not a perfect soldier, but a good man.”
NOTE: Most of this is just the plot of Captain America: The First Avenger.
Steven Grant Rogers was born on July 4, 1918 to Joseph and Sarah Rogers in Brooklyn, New York. However, Joseph was killed in action during World War I, just before Steve was born. Raised by his mother, Steve grew up to be very resilient and strong-willed, though he was of smaller stature and weaker constitution than most boys his age. This tended to get him into trouble with people much larger and stronger than himself, as he was an easy target.
One day, when bullies tried to steal his lunch money, Steve was defended by James Buchanan Barnes --- commonly referred to as Bucky. This event led the two to become best friends over the following years.
Steve attended George Washington high school from 1932-1936, then Auburndale Art School from 1937-1938. However, in 1936, tragedy struck. Sarah Rogers, who was a nurse, contracted tuberculosis and passed away.
In 1939, when World War II was declared, Steve decided he wanted to join the United States Army. He trained himself (with help from Bucky) and visited several recruitment centers. But ultimately, each attempt was met by rejection. With his various health problems, Steve was unfit to serve.
But finally, after overhearing a conversation between Bucky and Steve detailing Steve’s desire to fight for his country, Dr. Abraham Erskine approached Steve to talk. After determining that Steve was the kind of man worthy of his project, Dr. Erskine approved his enlistment.
Steve was then shipped off to Camp Lehigh to train. There, he had difficulty keeping up with the other recruits physically, but he displayed great mental and moral strength. These were the qualities Dr. Erskine deemed worthy for project rebirth.
Once Steve had been selected for project rebirth, he was escorted to the experiment facility by Peggy Carter. Inside the facility, Dr. Erskine and Howard Stark prepared Steve for the procedure that would hopefully turn him into the world's first successful super-soldier.
The procedure was successful in turning Steve into a super-soldier, but Dr. Erskine was assassinated shortly after the process was completed.
Since Dr. Erskine was not able to oversee the project any longer, the government put Steve to work. Instead of sending him overseas to fight, he became an icon of propaganda --- Captain America. He encouraged people at home to buy war bonds and participate in the war effort any way they could.
However, Steve became very unhappy with his role in the war. While touring some base camps overseas, he learned that members of the 107th infantry, Bucky’s unit, had gone missing. Though he was told that Sergeant Barnes was presumed killed in action, he refused to believe it. So with Peggy and Howard’s help, Steve stole some weapons and infiltrated a hydra camp to find and rescue his best friend.
Once he frees the soldiers and brings them back to base camp, everything changes. Steve is asked to put together a team of men to fight with on the front lines, which would eventually be nicknamed the Howling Commandos. Together, the Howling Commandos went on to take down many hydra bases.
Unfortunately, during a battle on an armored train, Bucky was thrown over the edge onto the snow mountainside and presumed dead. This threw Steve a period of mourning.
Steve eventually led the charge on HYDRA’s headquarters and fought Red Skull (Johann Schmidt, the first man to be injected with the super-soldier serum) --- but he was unable to stop him from attempting to launch bombs at the major cities in the United States.
This led to Steve chasing Red Skull via aircraft. While the bombs were stopped, Red Skull escaped via tesseract portal, leaving Steve in the failing aircraft. To save New York City, Steve crash landed his plane in the Arctic Ocean, where he presumably died.
However, the serum kept Steve alive in the ice until S.H.I.E.L.D. Found him --- a total of 67 years.
TL;DR
Steve was small and scrawny until he was selected for project rebirth. The super-soldier serum made him stronger and he went on to become Captain America. At first, he was just an advertising icon. But then he became a real soldier. He saved the lives of many soldiers and civilians, but met his seemingly untimely demise in an emergency crash landing in the arctic waters. However, the serum kept him alive and he was found 67 years later. Now, he's adjusting to modern society while fighting crime with The Avengers.
More about Steve:
Steve is on the asexuality spectrum. He is biromantic, but does not feel sexual attraction often. When he does, it is because he has a deep emotional connection to that person. This is generally referred to as demisexuality. In verses where he has a romantic partner and they engage in sexual activity, he is demisexual. However, there may be verses where he is completely asexual.
In most verses, Steve is a virgin. He is not sex-repulsed, but he does get very flustered by the topic.
Steve sees a therapist for his PTSD and general anxiety.
His therapist recommended he get an emotional support animal, so he has a puppy! His name is Dodger, and you can read more about Dodger soon! (I’m working on his lil bio.)
Now, Steve works at the animal shelter where he adopted Dodger. He’s a volunteer and doesn’t generally have a set schedule. They basically call him in whenever he’s not busy and they need a hand.
BONUS: Stony Mixtape