I've added some more topics. I don't know if they're the broadest and most important, though. In many cases, I'm sure they're not, but I don't know which ones would be so considered. Please, please check and edit the entries in your areas of expertise. See talk:Wikipedia arranged by topic.
... and Moscow, Russia, with an inventory of 12,000 titles.
1904 in literature
1904 in music
1904 in sports
The second Summer Olympic Games are held in St. Louis, ...