South Pass, Wyoming is the gap through the Rocky Mountains that saw over 500,000 emigrants pass through on their way to settle the Oregon Territory, strike out for religious freedom in Utah, or pan for riches in California. The Oregon, Mormon Pioneer, California, and Pony Express National Historic Trails work together to tell the story of how the United States became a coast-to-coast nation. Much of the area has never been developed and it appears much as it did in the 1840s, 1850s, and 1860s. Over 10,000 graves line these historic trails, making South Pass a sacred site. But like much of the American West, South Pass is constantly under threat of development.