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.
... Reservation[?]
Kaibab Indian Reservation[?]
Fort Mojave Indian Reservation[?]
Colorado River Indian Tribes[?]
Chemehuevi Indian Reservation[?]
Fort Yuma Indian ...