Final answer:
The Donner Party got stuck in the mountains during their westward journey on the Oregon Trail due to inadequate supplies, delayed departure, and poor decisions.
Step-by-step explanation:
The group of individuals who famously got stuck in the mountains during their westward move due to their lack of supplies, late departure, and poor decision-making were known as The Donner Party. This tragic historical event unfolded as settlers were moving along the Oregon Trail and similar routes in search of new opportunities and land in the West.
The Donner Party's experience serves as a stark reminder of the challenges and dangers faced by pioneers during the era of westward expansion in the United States. Coordination and timing were crucial for successful travel, as well as cooperation and the need for adequate planning and supplies.