The change in US policy that decreased the population of buffalos in the 1800s was the increased hunting and killing of buffalos by settlers, hunters, and the US government. This was done to reduce the food source of Native American tribes who relied on buffalos for sustenance. Additionally, the US government actively encouraged the hunting of buffalos as a way to control and subdue Native American populations. This, combined with the expansion of railroads, agriculture, and the loss of natural habitat, led to a significant decline in the buffalo population from an estimated 30 million in the early 1800s to just a few hundred by the end of the century.
