Colorado is a state that encompasses most of the Southern Rocky Mountains as well as the northeastern portion of the Colorado Plateau and the western edge of the Great Plains. Colorado is part of the Mountain States, the Western United States, and the Southwestern United States. 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. Colorado is bordered on the north by Wyoming and Nebraska, on the east by Nebraska and Kansas, on the south by Oklahoma and New Mexico, and on the west by Utah. The four states of Colorado, New Mexico, Arizona, and Utah meet at one common point known as the Four Corners. Colorado is one of only three U.S. states with no natural borders, the others being neighboring Wyoming and Utah. Colorado is noted for its vivid landscape of mountains, plains, mesas, and canyons. The 30 highest major summits of the Rocky Mountains of North America all lie within the state. Colorado is home to 4 national parks, 6 national monuments, 2 national recreation areas, 2 national historic sites, 3 national historic trails, 1 national scenic trail, 11 national forests, 2 national grasslands, 41 national wilderness areas, 2 national conservation areas, 8 national wildlife refuges, 44 state parks, 1 state forest, 323 state wildlife areas, and numerous other scenic, historic, and recreational attractions. The United States Census Bureau estimates that the state population was 5,024,748 on July 1, 2009, an increase of 16.82% since the U.S. Census 2000. Denver is the capital and the most populous city of Colorado. Residents of the state are properly known as "Coloradans", although the archaic term "Coloradoan" is still in use.