The Spectre's career began in the early 1940s, when hard-boiled detective Jim Corrigan was murdered. His spirit survived, however, and it sought revenge against Corrigan's murderers in a grim, supernatural fashion.
During the mid-1940s, the popularity of superhero comics began to decline, and the Spectre suffered as a result. He was reduced to playing the role of "guardian angel" to a bumbling character called "Percival Popp, the Super Cop." The character had formerly been part of the Justice Society of America featured in All Star Comics, but he was replaced in 1944.
When the Silver Age of comic books arrived in the 1960s, the Spectre was re-written and returned to the role of an avenging undead spirit. His power was vastly increased, and at times he approached the level of omnipotence.
Among the many changes made to DC Comics' characters during the later half of the 1980s (following the Crisis on Infinite Earths), the Spectre was largely de-powered. He retained his role as a grim, avenging spirit; however, he was also retconned somewhat. More of the Spectre's "origin" was revealed, and readers learned that he was originally meant to exist as the embodiment of the "Wrath of God," and Jim Corrigan was only a part of him.
Eventually, Corrigan's soul went on to the afterlife. The role of the Spectre was assumed by Hal Jordan, the spirit of the former Green Lantern.