Archaeological Mysteries & Adventures

I'm a terrible sucker for PBS documentaries about archeology; Secrets of the Dead, Nova, etc. Just re-watched a couple that brought out conclusive evidence to show that the Spanish versions of how the Aztec and Incan empires were conquered is a bit of history being written by the victors and seriously downplayed the roles of the natives that helped them. It got me thinking about archaeological mysteries in the frontier as an adventure. Naturally you need an official version of history and then you need the truth. There has to be a reason that the truth os covered up. Two approaches can be taken: one is find a significant event in history and write in a back story or two write up an event that is not necessarily a pivotal historical event. The second approach is probably simplest as you don't have to worry about time line issues.