In 1942 a short time after Joe Simon and Jack Kirby created for Marvel Comics the hero Captain America, a surprisingly similar hero named Guardian joined the DC ranks. Similar to Captain America wherein he uses a shield and has no superpowers, Guardian first appeared in DC issue Star-Spangled Comics #7 (Apr 1942).
Guardian’s civilian identity is Jim Harper. Who was a police officer in Metropolis’ suicide slum district. He was trained to fight by ex-boxer Joe Morgan (the same trainer of Wildcat and the first Atom). Taking his training to the streets as Guardian, Jim Harper became a vigilante to catch crooks that the law could NOT prosecute.
The legal Guardian to a group of kids known as the Newsboy Legion. The boys of the Newsboy Legion grow up to become the founders of the Cadmus Project. Using their tech at Cadmus, they grow Harper a new, younger body and transfer his consciousness from his dying form into that new one. This allows him to continue fighting as the Guardian in a new era.
Jim Harper is later revealed to be the Great-Uncle of Roy Harper aka Speedy.