Jim Harper grew up as a poor boy in Metropolis' "Suicide Slum." He and his best friend Leo sometimes engaged in petty theft, but after one such act, Jim was caught by a man who called himself Nat Milligan. Leo got away, and JIm did not see him again for years. Milligan believed that boys could escape poverty through careers as athletes, and he trained Jim over the suceeding years in hopes of turning him into an Olympic champion. Later, Jim would discover this man was actually Joe Morgan, who had trained the original Atom and Wildcat.

Eventually, Jim Harper returned to suicide slum todiscover that Leo had become a gangster. When Leo was killed before Harper's eyes, Harper vowed to fight the way that Suicide Slum destroyed people's lives. He told Milligan thaht he was joining the police force and Milligan fell into despair at the thought of losing another protege.

As a rookie policeman, Harper was assigned to Suicide Slum. One day, while off duty, He was beaten up by vengeance seeking thugs. To protect himself, Harper obtained a costume, a helmet and an antique shield from a costume shop and, in costume, captured the thugs, who turned out to be wanted kidnappers.

The masked Harper called himself the Guardian, saying he was a "guardian of society."

Later, officer Harper captured four newsboys who were robbing a hardware store. To prevent them from being sent to an institution, Harper instead persuaded the judge to make him the legal guardian of the four orphans, who thereafter had many adventures as the Newsboy Legion. The boys often suspected that Jim was the Guardian but they were never able to prove it.

During World War 2, the Guardian was a member of the All Star Squadron. Harper eventually retired as the Guardian when he becam a polic detective. The Newsboy Legion members, now adults, went to work at the DNA project, a genetics laboratory. After being shot by a criminal, Harper confessed to the former Newsboys that he had indeed beeen the Guardisn. Harper died, but at the DNA Project, the Legionnaires made a clone of Harper that possessed his memories. This clone became the Golden Guardian.