Captain America is Steve Rogers, a Brooklyn-born soldier who was transformed by the Super Soldier Serum in 1943. This is the core identity across nearly all Marvel canon — comics, MCU films, and animated series. Here is what defines him:
Steve Rogers was a scrawny, sickly kid from Brooklyn who was rejected from military service during World War II due to his health conditions. Dr. Abraham Erskine, a scientist working for the U.S. Army, recruited him for Project Rebirth — an experimental program to create the perfect soldier using a Super Soldier Serum. The serum amplified everything about Steve: his strength, speed, durability, and healing factor — but it could not change his core character. That is the point. The serum gave him the body to match his already-heroic spirit.
Unlike most superheroes, Steve Rogers does not get his powers and become a hero. He was already a hero — he volunteered for a dangerous experiment to serve his country when he could have hidden. The serum just gave him the tools. His identity is built on conviction, not the costume.
Captain America has never really had a secret identity in the traditional sense. The world knows Steve Rogers is Captain America. There is no Peter Parker / Spider-Man split where he hides from the public. His struggle is not about keeping the identity secret — it is about being a man out of time (in the MCU, he was frozen and woke up 70 years later) trying to find his place in a world that has moved on without him.
Pro tip: The most interesting version of Captain America is not the invincible soldier — it is the guy who questions authority and stands up for what is right even when his government tells him not to. Watch or read Civil War (the story, not just the movie) to see why Steve Rogers is such a compelling character. His identity crisis is philosophical, not about masks.