The names of the creators of most long-running comics are well known. Jerry Siegel and Jerome Schuster created Superman; Bob Kane created Batman; Stan Lee and Jack Kirby created most of the Marvel superheroes. But one of the greatest of comic creators, a man whose output ran into thousands of comics, is often overlooked. That man is Gardner F. Fox.
Fox grew up in Brooklyn and went to college to get a law degree. However, during the Depression, he realized he needed to supplement his income, so he began writing, hooking up with DC Comics and writing stories almost from the beginning of comic books. He quickly became a top writer for DC, since he wrote well and met deadlines. His first assignments was on the long-forgotten Speed Saunders, but he very quickly started writing for Batman, where he reached comic book immortality in his first story, where he created the utility belt.
At about the same time, he created his first well-known characters, the Sandman. This isn't the same one Neil Gaiman made famous, though Gaiman did include references to the original, but it was successful enough.
He came into his own in 1940, when he developed the Flash. The idea of a fast-running superhero caught people's imagination* and the Flash became one of the stalwarts of the Golden Age of comics. He followed that up with creating another of the great names of DC comics: Hawkman. Other characters followed, including Dr. Fate and Starman (co-creator of both).
These read like a roll call of all the great characters of the 40s, but soon Fox topped them all by the simple expedient of showing them all together. Taking a group of characters from All-American Comics,** Fox put them all together and created the Justice Society of America. He wrote most of the JSA stories, and made it into one of the great name of the Golden Age.
But the Golden Age ended and the comics began to suffer. Fox switched from superhero strips to western and science fiction comics and managed to keep working during the hiatus after Seduction of the Innocent.
But Fox wasn't through with superheros. In the mid-50s, when editor Julius Schwartz decided that the time was right for more superhero comics, one of the first people he contacted was Fox, who helped with the revamp of the Flash, Hawkman, and the Atom and eventually, wrote the new version of the Justice Society, the Justice League. He also came up with the Earth-1 and Earth-2 concept, which allowed the heroes from the Silver Age (Earth-1) to interact with the heroes of the Golden Age (Earth-2) to meet and interact.
Fox's interest in science fiction also continued, and he wrote many of DC's SF titles, eventually creating their best-know SF heron, Adam Strange, in 1958. In the 60s, he went back to writing Batman again, taking two obscure Golden Age villains -- the Riddler and the Scarecrow -- an turning them into important members of the Batman's rogue's gallery.
Fox left DC in 1968 over a dispute about benefits, and did a little bit of comic book work, but primarily wrote SF novels full time.***
Over the years, Fox wrote an estimated 4000 comic book stories**** and he was revered in the field. So much so that when they created a new Green Lantern, he was named Guy Gardner in his honor.
Fox worked regularly up until his death in 1985. His work is a bit dated, and even silly today, but that's due to a change in critical opinion, not because they weren't good stories in their time. Probably no one else wrote more comic books.
*Even though the original story was awful by any measurement, other than the concept of the character.
**A part of DC, which in that time was split between All-American and National Periodicals Publications. Eventually the two merged into National Periodicals, which became DC, the letters coming from their oldest title, Detective Comics.
***One of his novels, Escape Across the Cosmos was actually plagiarized twice and published as Titans of the Universe and Star Chase by different authors.
****The Grand Comics Database lists well over 3000, and there were probably more, since he was often uncredited.