Without wanting to discourage further answers, you might be interested in How did the concept of "fandom" emerge? Is it a 20th century phenomena or does it have a longer historical legacy? and The first geek "fandom" arose around Hugo Gernsback's sci-fi pulp magazine, Amazing Stories. Fans would trade letters, publishing their addresses in the magazine. How did this proto-geek cuture arise? Were there other fan groups which focused on radio or comic strip content?