What was the biggest threat the Corps of Discovery faced as they climbed the Rocky Mountains?

The biggest threat the Corps of Discovery faced while climbing the Rocky Mountains was the harsh and unpredictable weather, which included extreme cold, snow, and difficult terrain. These conditions made travel challenging and posed risks of frostbite, exhaustion, and food shortages. Additionally, the potential for encounters with hostile Native American tribes added to their dangers. Overall, the combination of environmental challenges and interpersonal conflicts heightened their perilous journey.