“Robinson had originally planned to include American frontiersmen like Lewis and Clark and Native Americans, including Sacagawea. But Borglum, eyeing an opportunity to make a national statement, dissuaded the historian. Instead they settled on the four American presidents, two of them slaveholders and all of them viewed by Native Americans as racist.” 
> Native Americans have always contended that the Black Hills of South Dakota belong to them, and that the sacred land was stolen after gold was discovered there. In 1980, the Supreme Court agreed, ordering the federal government to compensate eight tribes for the seizure of Native land.
I don't think enough people know this. Or know that the tribes refused the money saying they would only accept the return of their land. The money currently sits in an account gaining interest and is over a billion dollars.
I personally hope someday this land is returned to them and Mount Rushmore is removed (possibly preserved as history if technologically possible) much as we do with Confederate monuments.
And regardless, this has nothing to do with the US government signing a treaty giving the Black Hills to Lakota "forever" and then just a few years later driving them off the land. The US government itself says what it did was illegal by its own laws.