Three miles east of Chadron, Nebraska, the Museum of the Fur Trade occupies what was once James Bordeaux’s trading post, established for the American Fur Company in 1837. Today, visitors can walk through a reconstructed version of the trade site that was built on the original foundation stones and postholes.

The site’s story is bigger than a simple log outpost on the plains, however. In the aftermath of the Civil War, conditions on the Northern Plains became unstable, and trade often degenerated into the supplying of contraband arms to Native Americans resisting government-issued removal. Eventually, in 1876, army troops confiscated 40,000 rounds of Winchester ammunition at the post to keep it from being sold to the Lakota fighters resisting U.S. military campaigns.

Today, the Museum of the Fur Trade displays more than 6,000 original artifacts—the most comprehensive collection of historical pieces from the fur trade period in the world.…