The western region of the United States is the largest region of the country, covering more than half of the approximate land area. Land included in the western region was acquired in different ways, including the Louisiana Purchase, the Gadsden Purchase, the addition of the Republic of Texas, and lands ceded by both Mexico and Britain.
The geography of the western region includes rainforests, plains, mountains, prairies and coastal areas. The western region includes 13 states which include eight Mountain states and five Pacific states. The Mountain states are New Mexico, Arizona, Utah, Nevada, Montana, Wyoming, Colorado and Idaho. The Pacific states include Alaska, Hawaii, California, Washington and Oregon. Texas and Oklahoma, while traditionally associated with the west, are considered southern region states.
Major population centers include San Diego, San Francisco, Los Angeles, Seattle, Portland, Denver, Phoenix, Colorado Springs, Honolulu, Tuscon, Billings and Las Vegas. Los Angeles and its surrounding areas maintained the largest population in the western region as of 2013. Nevada, Alaska, Washington and Wyoming all do not have a state income tax as of 2013. Politically, the majority of the western region is historically democratic. Interior areas, particularly the Mountain states, historically lean more toward voting Republican.