As with most of the North American continent, this area had been occupied by indigenous people for thousands of years prior to European exploration and colonization. The descendants of these indigenous people, known as Native Americans, Alaska Natives and Native Hawaiians, are comprised of many different tribes with their own languages and cultures and still exist in these areas today.

The states that comprise the Western United States were explored by European countries beginning in the 16th century and were all claimed by other countries until the 19th century. Spain, France, Britain, Mexico and Russia all claimed parts of the what is now the western United States. Through treaties, purchases and war these lands were all under the jurisdiction of the United States by the late 19th century.