Here's why:
* Abundance: The American Bison (buffalo) were incredibly abundant in the 19th century, often numbering in the millions. They were an easy target for hunters, especially from moving trains.
* Accessibility: The railroads opened up vast stretches of the West, making it easier for hunters to access areas where buffalo roamed.
* Market demand: Buffalo hides were in high demand for leather goods, and their meat was a source of food for both the growing population and for the railroad workers.
* "Sport hunting": While hunting for food and resources was important, there was also a growing culture of "sport hunting" among wealthier individuals, who saw buffalo as a trophy to be killed.
This combination of factors led to a massive decline in buffalo populations. The railroads, with their speed and accessibility, played a significant role in this tragic event.