The Sangre de Cristo Mountains played a significant role in the history of the United States. Fort Union, manned by volunteers from New Mexico and Colorado territories, was the site of the first significant defeat. These mountains were also the backdrop for travelers and explorers, and were a source of valuable resources like gold, silver, copper, iron, and zinc. The Sangre de Cristo Mountains also served as a natural border between different regions, including the mesa country and the tropical regions. They were a symbol of both beauty and danger, with their towering peaks and unpredictable weather, proving to be a formidable obstacle for many.