In the wake of DC's announced relaunches of its whole line in September, news of another numbering change, this time to Uncanny X-Men, a survivor of past relaunches. David Uzumeri at Comics Alliance writes that "as a consequence of the events of Jason Aaron's X-Men: Schism event series, the stalwart title will end as of October's #544, giving the crown of longest-running uninterrupted title at the Big Two to... Vertigo's Hellblazer, of all the unlikely winners." Hellblazer was at #278 in April.
Increasingly in American comics, longevity records are a complicated matter. Uzumeri is speaking only of Marvel and DC, of course, but there are complications even then. Untouched by the 1990s relaunches, Uncanny X-Men did become our poster-child for a Marvel title untouched by renumbering — but even then, we were having to be careful not to use the phrase "continuously published." Uzumeri was careful to avoid it in his piece, but it is worth a refreshing of the collective memory that the title does have a couple of blips, one of them fairly large.
We'll set aside for a moment the title change from X-Men to Uncanny X-Men that happened in #142 — yes, the cover logo had changed much earlier, but in comics collecting it's what's in the indicia that historically has counted. We can also probably ignore the four months the title wasn't on the racks during the "Age of Apocalypse"; the subscribers received the four copies of Amazing X-Men, which it effectively became for that period, and they continued to receive Uncanny immediately after the event ended. The main title was neither renumbered nor taken out of production. The bigger interruption, though, came in 1970. X-Men was off the shelves for nine months between issues #66 and #67, a hiatus after which it returned as a bimonthly reprint series.
So we would give Uncanny the Big Two record for uninterrupted numbering up until September; Hellblazer, going since January 1988 does not, at a glance of my records, have any similar production breaks, and would have the claim for the Big Two — except that Mad, which began as an E.C. comic book and is now published by DC, is on issue #509. Once again, quibbles enter: it's not comics throughout, and it's been magazine-sized for decades, since #24. I tend to think it should be included, but it would have a clearer claim if we change our term to "comics publication" — as opposed to the traditionally sized comic book.
Again, as we're talking about unbroken numbering and not publication, that lets out the Marvel titles that will remain in the 600s after Uncanny and DC renumber; Amazing Spider-Man, Tales of Suspense/Captain America, Journey Into Mystery/Thor, and Tales to Astonish/Incredible Hulk all were renumbered (not to mention renamed, in the latter three cases). In the Amazing Spider-Man case, the series did continue in production the entire time, with subscribers receiving books continuously despite the renumbering; I suspect that's being done with Fantastic Four/FF, but it gets a bit harder to argue that it's the same title when there's a name change and a renumbering. Amazing X-Men was not counted in the Uncanny numbering, nor was Amazing Scarlet Spider counted with Amazing Spider-Man.
What beats Hellblazer if we go beyond the Big Two? Archie, at #620, would be our candidate for unbroken publication; it was only quarterly when it started in 1942 and it wasn't always monthly afterward, but at a glance I'm not seeing any big gaps. If we allow for hiatuses, then we go with Walt Disney's Comics & Stories, which released #715 in January from Boom, latest in a line of publishers that includes Dell, Gold Key/Whitman, Gladstone, Disney, Gladstone again, and Gemstone. I haven't heard whether the restaurant giveaway Adventures of the Big Boy, which was in the low 500s in the mid 2000s, is still in production.
Detective Comics will of course remain the longest-running continuously published American series regardless of numbering — DC, Marvel, or anyone else — although it's interesting to note that Action has had the higher numbering for many years. Action passed Detective in the 1970s, following a bimonthly stretch for Detective — and then it leapt ahead during its year as Action Comics Weekly.
The highest-numbered continuously published American comics-related publication is Comics Buyer's Guide, with #1678, its 40th anniversary issue, now on sale. And going beyond the United States takes us into the weekly comics overseas — and some really high numbers!