The Rendezvous was a significant event and location for the Mountain Men in the early 19th century. It was primarily where the Mountain Men came together annually to trade beaver pelts for supplies, weapons, and other goods. This gathering involved various trappers, traders, Native Americans, and other frontier folks.
Among the options you provided, the last one is the most accurate: "It was where the Mountain Men traded beaver pelts for supplies and where they had fun and games." These gatherings included not just trade but also social interactions, festivities, and entertainment, reflecting the complex social fabric of the fur trade. The Rendezvous was crucial for the Mountain Men as it represented a critical opportunity to obtain necessary supplies and connect with others in the fur trading economy.