That requirement was the lock on the door.

It meant that even if some Sioux leaders could be persuaded to sign away land, those signatures would be legally meaningless unless backed by a three-fourths majority of adult Sioux males.

It was a structural protection against precisely the kind of manipulation that the history of American-Native treaty negotiations had repeatedly demonstrated was possible.

Six years after the treaty was signed, the lock was picked open with a different kind of instrument.

The Expedition That Changed Everything

In the summer of 1874, Lieutenant Colonel George Armstrong Custer led a military expedition into the Black Hills.