Note: Linked issues contain more information on the cancellation and relate to the Implosion only. The first issues of the Explosion are also linked. Do not link more issues to this concept.
In the early 1960s DC Comics was the industry leader in comic sales, but by the end of the 1960s, Marvel had seen a resurgence under Stan Lee and was gradually gaining more popularity. By the mid-1970s Marvel had successively overtaken DC Comics on the comic book market. One of the ways in which this occurred was through the maintenance of numerous titles. DC Comics noted this trend and attempted to regain their market share by undergoing an expansion of their own, in a venture known as the DC Explosion. DC expanded its lineup by 57 titles and corresponded this with an increase in cover prices.
Many new series were brought back which had been canceled in the 1960s and 1970s and many new series were planned as well. Between 1975 and 1979 DC unleashed 57 new titles. Notable among these series was the Vixen, which would have been the first series to have an African American female at its lead.
In the end the venture was mostly a failure. DC Comics continued to have poor sales and so in 1978 the editorial decision was made to cancel a majority of the titles, a decision which many fans subsequently called the DC Implosion (DC Comics does not refer to it as such.) Although the quality of the new issues was partially to blame, some have argued that other effects resulted in the decreased sales. These include blizzards in 1977 and 1978 which made distribution more difficult, and the ongoing effects of a weak economy and inflation which made the higher cover prices even less desirable.
Many of the characters persisted longer than the implosion and many stories were later printed in one form or another. One of the major ways in which this was done was in a limited release series called Cancelled Comic Cavalcade (a play on a previous series named Comic Cavalcade). This contained a wide range of material, some finished, some in rough sketches, and this was primarily created to establish copyrights over the material. In other cases stories were later published elsewhere. Some of these were in other collections, or in reworked stories. For instance, Secret Society of Super Villains #16 was later reworked into Justice League of America #166-168.
Among the cancelations there were 11 other series canceled which were not actually part of the Implosion. Most of the Implosion series ended abruptly, with little to no resolution to ongoing storylines and many promising continuation in the following month. These 11 series though were planned to end on schedule.
One of the notable decisions made at the time was to save the long running title Detective Comics. At the time this was far outsold by Batman Family. After negotiations, it was decided to save the long running title and to maintain the continuity of the series which DC Comics is named after. This had the unforeseen effect of canceling a popular series to merge it into another. Detective Comics would have been canceled at issue #480.
Following the editorial decision in 2011 to relaunch the entire DC lineup into the New 52, some references were made in the media to this previous expansion and contraction.