What was the true explorers of the Western mountains who opened new routes for settlers were the?

The true explorers of the Western mountains who opened new routes for settlers were primarily figures like John C. Frémont, Kit Carson, and Lewis and Clark. Their expeditions mapped out critical pathways through the Rocky Mountains and the Sierra Nevada, providing vital information for future settlers and travelers. These explorers not only charted new territories but also documented the geography, resources, and Native American cultures they encountered, significantly influencing westward expansion in the United States.