In a post earlier today (with 6 cool Mexican Spider-Man covers), I briefly summarised the obscure history of Spider-Man comics made and published in Mexico. That comment got a lot of upvotes and several people wanted to know more. I've done some more digging and realised that my comment didn't cover the whole story and was slightly wrong... so here's the full history with lots of great pics!
Amazing Spider-Man #1 was published in March 1963. Within 3 months, this issue was translated and reprinted in Mexico under the title *El Sorprendente Hombre Araña" by the publisher La Prensa.
Spidey was an instant hit in Mexico, and La Prensa continued to publish Spanish translations of Amazing Spider-Man. There was sufficient demand for a weekly title, but the US comic only came out every month or so. Initially, La Prensa translated and reprinted other, similar Marvel titles like The Avengers and Tales to Astonish, see here and here. However, these titles weren't as popular as Spider-Man.
La Prensa wanted to do their own Spidey comics for the Mexican audience. Here's where things get a bit murky. Some sources indicate that Marvel gave La Prensa permission to do write their own Spidey comics, whilst other sources say that La Prensa didn't get permission and just decided to publish their own stories anyway. I've seen references to Marvel editorial specifically stating that these comics were unauthorised, but I can't find the statements themselves, so I'm not sure what to believe. Anyway, starting with #123, La Prensa went ahead and made their own Spidey comics - mostly written by Raúl Martinez and drawn by José Luis González Durán. This means there's a whole bunch of unique Mexican stories - unfortunately I've only been able to find the covers online. Here's a gallery of the unique Mexican covers from 123-139: https://imgur.com/a/3hTef Some of the covers clearly just re-use Romita's interior or cover art, whilst others have been done from scratch for the Mexican series.
Until issue #144, the series went back and forth between US reprints and unique Mexican stories. However, the series started to focus more and more on Mexican stories - between #145 and #185 there were just 6 US stories against 35 Mexican stories. Here's a full list of the issues published by La Prensa: ("Cómic hecho en Mexico" means "Made in Mexico")
http://www.kingdomcomics.org/spiderman.html And here's a full gallery of the covers from #146 onwards:
https://imgur.com/a/s45ui Unlike the earlier covers, there's no obvious rip-offs - these are unique covers (apologies for the poor quality of a few of them). Some of the covers are really cool and quite different to the US ones at the time.
I have only read a few of the unique Mexican Spidey stories. As far as I know, no English translation exists, and the comics themselves are pretty rare. As indicated by the earlier post and as is clear from the covers, the biggest difference between the US and Mexican stories is the focus on Gwen Stacey. Gwen is drawn... well... take a look for yourselves! From what I've read, she was also a major focus of the Mexican stories, even moreso than in the US stories.
La Prensa lost the licence in 1974 and OEPISA started printing Spidey comics instead. One forum post I found said that La Prensa lost the licence because it was making and publishing its own, unauthorised Spider-Man comics, but my main source (the excellent Spider-Mex website) doesn't say anything about that. The La Prensa comics go up to #185, with the last translated/reprint being Amazing Spider-Man #120. As I'm sure most of you know, Gwen Stacey was killed in Amazing Spider-Man #121. This means that the La Prensa comics ended just before Gwen was killed - as far as I can tell, this was a complete coincidence, and La Prensa didn't give up the licence just because it's favourite character was killed off!
That's all I've been able to dig up for now. If anyone has any questions, please do ask because I've not put everything down in this post (it was getting too long).
TL;DR - about 45 unique Mexican Spidey stories were published in the 1970s, which focused a lot on Gwen Stacey and had some really cool covers