But many others have fallen into obscurity: Dollman, Blue Beetle, Amazing Man, Electro, Black Marvel, Hourman, Bulletman, Uncle Sam, the Red Tornado, the Black Terror, Professor Supermind, Wildcat, Mr. Terrific.
They acquired their superpowers in various ways, through super-secret experiments, weird meteors, radioactive spiders, and mystics from the Himalayas, but they all were dedicated to fighting Nazis, and they all had spectacular physiques, which they usually displayed in skin-tight spandex.
Here are some superheroes who appeared without a costume, revealing their massive pecs and washboard abs to brighten spirits during the dark days of the War:
Samson, the descendant of the Biblical hero, has super-strength, as long as no one cuts his long hair. He first appeared in Fantastic Comics #1 (1939), and got his own short-lived title in 1940. The kid, by the way, is his teen sidekick David (no relation to the Biblical hero).
The Ultra-Man, aka Gary Concord, premiered in All-American Comics #8 (November 1939). He's a 20th century scientist who goes to the future, aka Buck Rogers, and fights the tyrant Reborrizon. Later he's killed himself, but his son takes over as the new shirtless Ultra-Man.
Scrounging around for ancient, Biblical, and mythical superheroes, Dan Zolnerowich stumbled upon Hercules. Joe Hercules, however, is not descended from anybody. He's a "real American youth" who just happens to have super-strength. He starred in 21 issues of Hit Comics, from July 1940 to April 1942.
Magic Morro's story begins in Super Comics #27 (August 1940). Originally Jack Morrow, he gained his superpowers on an island in the Pacific, where of course one must go shirtless.