Has anyone ever found out where the Great Ghost Dance ritual actually took place? And where was it hinted in any of the books that the GGD was a blood magic ritual?

Most information I can find in one place about the Great Ghost Dance is Harlequin's oration in Harlequin's back. He talks about many people dying to power the ritual. He gives the speech at the site of the GGD, which is out in the desert. I couldn't find any actual hints as to where, but I assume it's Northwestern/Mid-western.

The Sectets of Power novel trilogy, specifically the third one, IIRC, gives a lot of info on the GGD. In fact, in the book, they pull off another one (yeah...) and show quite explicitly that the ritual is fueled by human sacrifice.
There's also passing menton in some later novels, like the unfogivegettable Dragonheart trilogy, plus some other books.

If you mean rulebooks, though, I'd also say that the Harlequin campaigns are your best bet.

Oh Sir Twist...it's been forever and a half since I thought about him.

So Harlequin was involved with the Great Ghost Dance? Did he teach the ritual to Daniel Howling Coyote, then?

No and no!

No, but some other IE did. And not the one who was Leonardo da Vinci...

A half-IE-half-The-Enemy, IIRC.

Aina's son, iirc.

It'd be some nice irony if the Great Ghost Dance took place at Wounded Knee, but in the Shadowrun rules, Wounded Knee would probably have a pretty hefty background count, preventing significant magic from happening there.

Quite to the contrary, if you know the aspected background count rules. "Freeing native americans with shamanistic magic" would certainly qualify for a hefty bonus there.

Definitely this.

Well, the (now former) Ute Nation was the place that was top of teh list in terms of where it likely happened. Many discussions about how screwy the weather was there, as well as the mana issues, pretty much pegged it, tho not to any *exact* location.

So, "Somewhere in Ute Territory" is a pretty safe bet.