The Atom first appeared in All-American Comics #19 (October 1940) and was created by writer Bill O'Connor and artist Ben Flinton.

[3] In winter 1940, the Atom also began appearing in All Star Comics as a member of the Justice Society of America, beginning with issue #3.

[3] Initially a proverbial 98-pound weakling, bullied at school and unable to impress the girl of his dreams, Mary James, the 5 ft 1 in (1.55 m) Al Pratt was trained to fighting condition by ex-boxer Joe Morgan (the same man who trained Pratt's fellow mystery men Wildcat and the Guardian).

In All Star Comics #3 (Winter 1940), the Atom describes himself to his fellow JSAers as "Al Pratt, a quiet sophomore at Calvin College".

[1] According to Jess Nevins' Encyclopedia of Golden Age Superheroes, the Atom "fights the Emperor of America, agents of the Black Dragon Society, and the Carnival of Crime, in addition to the Cootie Gang, Mandini the Magician and the scavenger Undersea Raiders".

[4] In 1948, the Atom gained super strength as a result of the latent effects of his 1942 battle with the reluctant supervillain Cyclotron (after whose costume Pratt redesigned his own).

Later it was revealed that a special Senate investigation panel had moved to obtain the identities of all active superheroes, at which point virtually all members of the Justice Society retired.

Al was depicted as a short, stocky, balding man with radioactive, super-powered hands and a body aged to about 60 years or so.

He was also written as a man more interested in training the next generation of heroes than "running off on crazy super-hero missions" (issue #2), though he still was hotheaded.

[19] This version is Albert Rothstein's uncle and a former member of the Justice Society who previously operated as Atom Smasher before passing the mantle to him.

[20] Al Pratt / Atom appears as a character summon in Scribblenauts Unmasked: A DC Comics Adventure.