First visited by Spanish explorers in the 1500s, the territory was claimed for Spain by Juan de Ulibarri in 1706. The U.S. obtained eastern Colorado as part of the Louisiana Purchase in 1803, the central portion in 1845 with the admission of Texas as a state, and the western part in 1848 as a result of the Mexican War.The state was named for the Colorado River, which early Spanish explorers named the Río Colorado for the red colored (Spanish: colorado) silt the river carried from the mountains. On August 1, 1876, U.S. President Ulysses S. Grant signed a proclamation admitting Colorado as the 38th state. Colorado is nicknamed the "Centennial State" because it was admitted to the Union as the 38th state in 1876, the centennial year of the United States Declaration of Independence. 
Breathtaking scenery and world-class skiing make Colorado a prime tourist destination. The main tourist attractions in the state include Rocky Mountain National Park, Curecanti National Recreation Area, Mesa Verde National Park, the Great Sand Dunes, Dinosaur National Monuments, Colorado National Monument, and the Black Canyon of the Gunnison National  Monument.