The hard-boiled private detective genre was a part of American popular entertainment for most of the 20th century. But it was during the middle years of the century, starting with Mike Hammer, created as Mike Danger by former comic book writer Mickey Spillane (who worked mostly for Marvel) that it achieved its greatest impact,with "hard-boiled dicks" in movies, on TV, in paperback books, and wherever else popular entertainment was purveyed. In comic books, they included Archie Comics' Sam Hill; Lev Gleason's Dan Turner, whose series ran in Crime Does Not Pay; and this one, Ken Shannon, who first appeared in the December, 1950 issue (#103) of Quality Comics' long-running Police Comics.
Ken's first story was titled "The Mad Irishman" — a typical way to emphasize the brutality of the "hard-boiled" characterization, later echoed in Johnny Dynamite's subtitle, "The Chicago Wild Man". The writer of that story is unknown, as are those of so many comic books of the period. The artist was Quality Comics regular Reed Crandall, whose later credits range from EC Comics to Treasure Chest.
The 103rd issue of Police Comics represented a complete departure from what had gone before. It had started as a typical 1940s comic book anthology, featuring superheroes like Firebrand, The Human Bomb and Phantom Lady. The only actual policeman in it was Harvey Kurtzman's Flatfoot Burns, whose adventures contained more slapstick than excitement. But by #102, the only superheroes left there were Plastic Man and The Spirit. #103 introduced two government-employed crime fighters, Inspector Denver and Treasury Agent Trask. But still, freelance crime fighters were more prominent, tho they dressed normally. Private Eye Dan Leary was also introduced in that issue, and Ken Shannon was featured on the cover.
That's not all. Less than a year later, Ken was featured in his own bimonthly comic. Ken Shannon #1 was dated October, 1951. He and his typically-tough secretary/receptionist, fiery redhead Dee Dee Dawson (surely, no relation to Dexter's sister Dee Dee) shared that title for ten issues, ending in April, 1952, as well as continuing to appear in every issue of Police Comics. Ken continued to occupy the cover, too, on every issue he was in except the last, #127 (October, 1956).
After that, Police Comics folded — only two months before Quality Comics itself bit the dust. Many of its properties were acquired by DC Comics, which continued to publish Blackhawk, G.I. Combat and a couple of others, but let the rest fall into oblivion. Years later, DC revived many of Quality's characters, some of which became regulars, either in supporting roles or as part of its 1970s title, Freedom Fighters. But many, including Marmaduke Mouse, Bozo the Robot and Ken Shannon, were never seen again.