What caused the near extinction of buffalo by 1870?

The near extinction of buffalo by 1870 was primarily driven by the expansion of the railroad, which facilitated mass hunting of the species. The increase in transportation networks allowed hunters to access previously remote areas where buffalo herds roamed. Railroads also promoted the commercial demand for buffalo hides, meat, and other products, leading to a significant uptick in hunting activities. This phenomenon was exacerbated by the idea of "hunting for sport," as affluent individuals would shoot buffalo from moving trains.

Overhunting by Native Americans, while it did occur, was not the main factor contributing to the massive decline during this specific period. Native American tribes relied on buffalo for sustenance, but their hunting practices were sustainable and balanced with the buffalo population. The other factors, such as climate change and diseases spread by livestock, did have impacts on buffalo populations but were not the primary drivers of their near extinction. The railroads' role in facilitating widespread hunting was the most significant contributor.