Western United States

The western part of the United States, commonly associated with the Pacific Coast, the Rocky Mountains, and adjoining states. Its boundaries vary by historical, cultural, and administrative usage.

Pacific Coast: The western shoreline of North America along the Pacific Ocean. California, Oregon, and Washington give the region its Pacific-facing edge.
Louisiana Purchase: The 1803 U.S. acquisition of a vast territory from France, doubling the nation’s area. It opened much of the land later incorporated into the western United States.
Colorado River Compact: The 1922 agreement dividing the Colorado River’s water among seven U.S. states. Its allocations govern a crucial water source for the arid interior West.
Eastern United States: The eastern part of the United States, commonly associated with the Atlantic Coast and older centers of settlement. Its settlement history and coastal orientation contrast with those of the American West.
Indigenous peoples of the Americas: The diverse peoples whose societies originated in the Americas before European colonization. U.S. expansion across the West displaced Indigenous communities and contested their sovereignty.
Rocky Mountains: A major mountain system extending from western Canada through the western United States. The range forms a defining interior spine of the American West.
Oregon Trail: A 19th-century emigrant route from the Missouri River region to Oregon’s Willamette Valley. Its migration helped establish U.S. settlement in the Pacific Northwest.
Central Valley Project: A federal system of dams, canals, and aqueducts supplying water in California’s Central Valley. It shows how infrastructure supports intensive agriculture in a dry western landscape.
Midwestern United States: The central-northern region of the United States, commonly associated with the Great Lakes and Great Plains. Its agricultural and industrial identities differ from the West’s mountain and Pacific associations.
Indian Removal Act: The 1830 U.S. law authorizing the forced relocation of Indigenous nations from lands east of the Mississippi River. Its policies contributed to the displacement that preceded later western expansion.

Linked from 8 pages