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The Pacific Southwest is a region of the United States. In its broadest definition, it encompasses five states: California, Arizona, Hawaii, Utah, and part of Nevada. The region is one of cultural diversity seen all over. Several major urban areas lie within the region, including the San Francisco Bay Area and Salt Lake City. With the exception of Hawaii, four of the five states share similar historical backgrounds.[ citation needed]
There is no universally accepted definition of the phrase "Pacific Southwest." Whereas the related term Southwestern United States is generally used in a cultural or historical sense (for example, to refer to parts of the United States that were once part of the First Mexican Empire), the term "Pacific Southwest" is more commonly defined strictly by geographic or ecological factors.
For example, the American Society for Photogrammetry and Remote Sensing has a geographical application of the term, defining it as California, Arizona, Nevada and Hawaii.  The Fish and Wildlife Service, on the other hand, uses an ecological approach to define it as California, Nevada, and the Klamath Basin (which includes parts of Oregon). 
Ambiguity regarding the term is further compounded by the fact that even several United States federal agencies use different definitions. In addition to the Fish and Wildlife Service mentioned above, the Environmental Protection Agency defines Pacific Southwest as California, Nevada, Arizona and Hawaii , and the Forest Service defines it as California, Hawaii, and other U.S. islands in the Pacific Ocean .
- Los Angeles Pop. 3,792,621
- Phoenix Pop. 1,469,471
- San Diego Pop. 1,301,617
- San Jose Pop. 971,372
- San Francisco Pop. 805,235
- Las Vegas Pop. 583,756
- Tucson Pop. 520,116
- Sacramento Pop. 470,956
- Mesa Pop. 439,041
- Honolulu Pop. 337,256
Cultures combine and collaborate in the Pacific Southwest. Traces of the Old American West can still be seen in some areas, especially in the deserts. Hip-hop is one of the many cultures prevalent here, most noticeable in Los Angeles and the Bay Area. Polynesian culture flourishes in Hawaii, and Hawaiian Pidgin can still be heard in certain areas of the state. Spanish/Mexican culture is the most visible in the region, due to the fact four of the five states were once Spanish/Mexican possessions. Cowboys can be found anywhere in the Pacific Southwest. Hawaii has its own version of the American cowboy, the paniolo. Asian culture is demonstrated in the region, especially in California and Hawaii. The area also has a sizeable black population, along with Arabic and Jewish culture.
The Pacific Southwest contains a vast diversity in environments. Sub-arctic conditions are common in the high mountains of the region, such as on Mauna Kea. Rainforests can be found in certain areas of Hawaii.