Danny O'Hara was an orphan living on the streets of Depression-era Philadelphia when he was rescued from a gang of thugs by the hero known as The Fighting Yank. Feeling protective of the boy, and with no other options, the Yank took him under his wing and made him his crime-fighting partner.

As the All-American Kid, Danny aided the Yank in his fight against criminals and homebound spies during the early days of the Second World War. Eventually the duo confronted a criminal calling himself Doc Chronos, who claimed to be from the future. And during the fight, Chronos reactivated his temporal device, returning him to his own time. But both The Fighting Yank and Danny were caught in the temporal wake and pulled along with him. Now trapped 80 years in the future, the duo came to the attention of the team known as The First Guard, and were welcomed into their ranks.

Danny has adjusted quickly to his new situation, adapting to society and technology much faster than his partner. Recently, Danny and the Yank were approached by Agent Simon N. Kirby about Danny's need to continue his education, and against his will Danny began attending classes with other young costumed heroes including Kid Terror and Pollita. Together, these Junior G-Men stopped a criminal named Firebomb from destroying the United States Capitol Building.