According to the GAF poster, this info was revealed in 2004 alongside the game. But I was not aware of it. This info is certainly not part of their current screenshots, artwork, or ad campaign.
I STRONGLY RECOMMEND YOU DO NOT READ THIS
SPOILER LEVEL 1 (vague, yet still menacing):
spoiler (click to show/hide)
Bioshock is set in a specific alternate history. Beyond the obvious Rapture-building parts, that is.
(Spoiler Level 2 removed because I don't want to tell people even if they want to know.)
There are
spoiler (click to show/hide)
three endings
apparently, so I'm curious how to unlock them