It's been a while since I read anything from my collection of speeches given by famous native Americans, so I thought I would dip back into that.
In 1837-38, there was a terrible smallpox epidemic all over the Great Plains area. The inhabitants of Fort Union all got sick and it spread to the Mandan tribe, as well as several others. Smallpox decimated the Native American population, which had little immunity, and efforts to inoculate some of them failed. The Mandan tribe shrank from 2000 people to less than 150, and the chief, Mato Tope (The Four Bears) gave this speech shortly before his own death from the disease.
It's a tragic speech, given by a chief who is watching the destruction of his people. He understandably blames whites for the epidemic and encourages his tribe to rise up against them. As it turns out, the Mandan tribe had to combine with two neighboring tribes for survival and eventually became known as the Three Affiliated Tribes or the Mandan, Hidatsa and Arikara Nation.
A story has been spread that American soldiers deliberately infected the Indians with smallpox in 1837 by giving them diseased blankets. That story is apparently untrue; though it has been published by the well-known anarchist historian Ward Churchill, nearly all other historians disagree with his interpretation of the evidence. The sources do describe the people at Fort Union warning Native Americans not to venture near the fort and trying to inoculate them.
One of the most famous speeches by a Native American is Chief Seattle's 1854 Oration. It's often quoted, and so is a letter to President Franklin Pierce. However, as I looked into this speech's history, I found that it is almost certainly spurious. No original text can be found, and it was first printed 30 years later by Dr. Henry A. Smith, who doesn't seem to have attended any such event.
It's depressingly ironic that one of the best-known Native American speeches is almost certainly a fiction produced by a white man. There are many authentic records of eloquent Native American orations; we don't need to hang on to fakes.