Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
After hundreds or more westerns showing Native Americans as bloodthirsty savages and white settlers as peace-loving Christians, this was one of the first films to attempt to revise that view of history to show Native Americans in a sympathetic light as people with a right to their land who are fighting to protect it and their way of life from the whites who wanted to take it all from them and exterminate them. (The parallels to the counterculture and the Viet Nam war and its attrocities that had been recently revealed at the time the film was made were certainly very obvious back in 1970.) The film culminates with a very graphic and bloody depiction of the terrible 1864 Sand Creek massacre in Colorado where the Colorado Territory volunteer cavalry (an inexperienced force that had to defend the area because the US Army was fighting the civil war) killed over 500 Cheyenne people, half of them women and children, scalping, dismembering, and raping many of them. In the beginning we do see the Cheyenne massacre a group of soldiers to rob them of their gold, but the film's message is essentially very one-sided, verging on propaganda, as revisionist history of any kind tends to be in its infancy. But that didn't bother me near as much as the annoying opposites attract romantic comedy nonsense that took up half the film.
In the beginning of the film we see a very young Candice Bergan, 20 years before she was Murphy Brown, in a wagon surrounded by military troops who are escorting her. The camera switches to a long shot of them as they ride away then suddenly sinks down to ground level past the still bloody ribs and carcass of a cow down to a rattlesnake that is crawling under the skull. Then it cuts back to the soldiers. Unlike the average viewer, I'm usually too interested in the snake to wonder about why it's being shown, but I think that here the cringeworthy creepyness of the snake and the carcass for most viewers is meant as a sign that something bad is going to happen to these soldiers. And it certainly does.
The rattlesnake is not a species from the US. The film was shot in Durango, Mexico, so the rattlesnake they used is most likely a species of rattlesnake found in Mexico.