My understanding of 1920s-30s pulp fiction magazines like Weird Tales was that they were mostly a "boy's club": writers like Lovecraft, Howard, etc, who were also generally white. However, this seems to be an incorrect supposition on my part, as argued by sources like this, which is neat to learn.
Do we know anything about the gender and/or ethnic breakdown of early pulp magazines readers? E.g., did Weird Tales ever include surveys that people could respond to?
I talked about this a bit in my answer to What were the demographics of readers of Scifi like Astounding Science fiction in the thirties?, and I touched on this in a Tuesday Trivia answer on confession pulps where I noted that Peggy Fielding mentioned that True Confessions ran a 600-question survey on their readership in her book Confessing for Money.
Weird Tales never did any formal survey of readership; presumably they tracked subscriptions, but those files are lost. Most of what we can glean about female writers in Weird Tales is by tracing the bylines, with several prominent names like C. L. Moore, Greye la Spina, Margaret St. Clair and others that Terrence Hanley has been so good to write about on his blog; fans we mostly trace through 'The Eyrie' - the fan-letters page - and after editor Dorothy McIlwraith took the reins in 1940 the Weird Tales Club, which published fans' name and addresses. This gives us far from perfect data - men and women writers (and fans!) used pennames to conceal their identity for different reasons, published letters are a small fraction of readers which can be skewed by editorial fiat, and membership lists also only represent a fraction of the total readership. Damon Sasser had an essay on Women in the Weird Tales Club and estimates between 25-30% of club members had female names. For context, there were roughly ~500 member names published, and the circulation of the magazine was probably around 25,000-40,000 in the 1940s and 50s, possibly less.
The impression that the readers were primarily male - and primarily young - was a strong one, both among the pulpsters writing for the magazine and the editorial staff; Farnsworth Wright was sometimes afraid to offer more cerebral fare, and although the nude covers by Margaret Brundage were designed to titillate, they also sometimes (allegedly) drew the ire of Parent Teacher Associations (although I should add all such accounts I've read are scuttlebutt and never directly from Wright or anyone else at Weird Tales who would have been in a position to know such things).
Yet at the same time, there was always a female readership - and black fans, Hispanic fans, fans in other countries including Canada, the United Kingdom, Australia, South Africa, and even copies sold in continental Europe.