The Mississippi River serves as an unofficial divide between East and West in the United States. West of the Mississippi River are mountains, deserts, beaches and some of the nation's most culturally significant cities.
If the U.S. was divided in half width-wise in a precise manner, many of the states often considered to be Western states would be left out of the equation. That's why the Mississippi River is so significant as crossing this mighty river was a major event for early European colonists and American settlers moving westward from the Atlantic Coast. However, officially speaking, the U.S. government considers Alaska, Arizona, California, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington and Wyoming to be the West, which leaves out a few states immediately to the west of the Mississippi. Part of the reason the definition of "the West" is so nebulous is that it took decades after the official establishment of the U.S. as a nation for official territory to extend all the way to the Pacific coast.
Differences Abound in Western States Within this official Western region, geographic characteristics, such as climate, topography and vegetation, vary greatly, especially from the north to the south. The Pacific Northwest is characterized largely by mountains, dramatic rocky beaches and acres of old-growth evergreen forests, though the Eastern regions of Washington and Oregon both include plenty of flat, dry land and even desert. The northern parts of California share many of Western Oregon's traits but Southern California is dramatically different in terms of climate and vegetation, with inland areas featuring true deserts featuring cacti and vast stretches of desolate sand dunes. The coast in this part of California is much warmer and more traditionally beachy than northern parts of the Pacific Coast.
Physical Characteristics of the Western States Desert landscapes continue further east in the Western states of Nevada, Arizona and New Mexico, with parts of Utah and Colorado also boasting dry, rocky landscapes. Dramatic natural wonders, such as the natural landforms of Arches National Park and the Grand Canyon, add grandeur and beauty to this part of the West, and temperatures tend to be warmer in this part of the region than anywhere else. Things get colder moving northward into the mountain states of Idaho, Montana, Wyoming, Utah and Colorado, which boast several alpine areas thanks to the presence of the Rocky Mountains. Harsh winters and mild summers are common throughout most parts of these states, although each one features a fair amount of topographic diversity due to their large size.
Major Cities Beyond physical characteristics, the Western U.S. includes some of the largest cities in the nation, some of which are in California. Los Angeles, San Francisco, Seattle, Denver and Portland are all culturally significant cities in the U.S. However, in many cases, these cities are home to a different cultural atmosphere than the more rural areas outside of the cities. Many Western U.S. states are considered to be "blue" states, politically speaking, because these large urban centers outweigh the voice of more conservative voices from rural areas and small towns throughout the West. Without Portland, for example, Oregon would likely be a much more politically conservative state.