1. Name three factors leading to the decline of buffalo populations in the early to mid 1800s. 2. How does the Bent, St. Vrain, and Company contribute to the decline of buffalo herds? Objective Trace how trading during the fur trade era contributed to westward expansion and the decline of bison on the plains. Background Intro: Bent’s Fort began as a trading post in the southern plains on Cheyenne and Arapaho homelands during the 1830s. Although the fort began during the era of the fur trade, it did not center on beaver. The beaver fur trade had nearly ended by that time because the animal was Duration: 60 Minutes.