The Spirit chronicles the adventures of a masked vigilante who fights crime with the blessing of the city's police commissioner Dolan, an old friend. Despite the Spirit's origin as a detective named Denny Colt, his real identity was virtually unmentioned again, and for all intents and purposes he was simply "the Spirit". The stories range through a wide variety of styles, from straightforward crime drama and noir to lighthearted adventure, from mystery and horror to comedy and love stories, often with hybrid elements that twisted genre and expectations.
The feature was the lead item of a 16-page, tabloid-sized, newsprint comic book sold as part of eventually 20 Sunday newspapers with a combined circulation of as many as five million copies. "The Spirit Section", as it was colloquially called, premiered June 2, 1940, and continued until October 5, 1952. It generally included two other, four-page strips (initially Mr. Mystic and Lady Luck), plus filler material. Eisner worked as editor, but also wrote and drew most entries — generally, after the first few months, with such uncredited collaborators as writer Jules Feiffer and artists Jack Cole and Wally Wood, though with Eisner's singular vision for the character as a unifying factor.
Sources: Wikipedia, the free encyclopedia