Colorado, which joined the union as the 38th state in 1876, is America’s eighth largest state in terms of land mass. Located in the Rocky Mountain region of the western United States, the state’s abundant and varied natural resources attracted the ancient Pueblo peoples and, later, the Plains Indians. First explored by Europeans in the late 1500s (the Spanish referred to the region as “Colorado” for its red-colored earth), the area was ceded to the United States in 1848 with the Treaty of Guadalupe Hidalgo that ended the Mexican-American War (1846-48). In 1858, the discovery of gold in Colorado attracted new settlers. During the Plains Indian Wars (1860s-80s), Colorado’s wild frontier was the scene of intense fighting between Native Americans and white settlers. In the 21st century, Colorado continues to rely on its natural resources as well as agriculture and tourism to sustain its economy.