September 3 is the anniversary of The Harney Massacre. This was a US terrorist attack made in "retaliation" for The Grattan Fight the year before. It saw the slaughter of almost a hundred native men, women, and children at the hands of General Harney and his gang of murderers.

When the band saw Harney's men approaching, they attempted to surrender. Harney ignored this, and opened fire. The fleeing people were driven toward his cavalry, where they were cut down en masse. One of the soldiers present had this to say:

The sight on top of the hill was heart-rendering, wounded women and children crying and moaning, horribly mangled by bullets… I found another girl about 12 years old laying with her head down in a ravine, and apparently dead. Observing her breath, I had a man take her in his arms. She was shot through both feet.

Harney however, had this to say:

I have come to kill Indians, and believe it is right and honorable to use any means under God’s heaven to kill Indians. Kill and scalp all, big and little; nits make lice.

The US leadership responded to this blatant act of genocide by naming the tallest mountain in South Dakota after him, along with a plethora of rivers, lakes, streets, and other geographical locations after him.