The "West Coast", "Western Seaboard", or "Pacific Seaboard" are terms for the westernmost coastal states of the Western United States, comprising most often California, Oregon and Washington. Arizona and Nevada, while not coastal states, are also often included in the West Coast due to their proximity to the Pacific Coast and their economic and cultural ties to California (such as Arizona's two largest universities which are members of the Pacific 10 Conference). Although not part of the contiguous United States, Alaska and Hawaii do border the Pacific Ocean and could be included in the West Coast. As of 2007, the estimated population of the West Coast ranged from approximately 50-60 million, depending on which states are included in the estimate.

An older term, thought to have arisen in the Northeastern United States, refers to the West Coast simply as "the Coast." The West Coast can also be referred to jokingly as the "Left Coast", a pun based on its lefthand position on a north-centric map of the U.S., as well as its reputation for being more politically liberal (or "left-wing") than some other parts of the United States.

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