Western vs. Eastern North America: Where Are the Mountains?

Short answer: The West wins by a landslide. But the geological reasons tell a continent-scale story.

The Western Cordillera

A near-continuous chain of ranges runs from Alaska to Mexico:

• Rocky Mountains – 3,000+ miles, Canada to New Mexico; peaks over 14,000 ft (Colorado's "Fourteeners").
• Sierra Nevada – California's granite spine; Mt. Whitney (14,505 ft), highest in contiguous US.
• Cascade Range – Volcanic arc from BC to Northern California; Rainier, Shasta, St. Helens.
• Coast Ranges, Wasatch, Uinta, Sangre de Cristos – Dozens of sub-ranges.

Tectonics drive it all: the Pacific Plate subducting under North America, plus Basin and Range extension.

The Eastern "Mountains"

Appalachian Mountains – Ancient (480+ million years), eroded, lower. Highest: Mt. Mitchell (6,684 ft). Once Himalayan-scale; now rounded, forested ridges.

Adirondacks (NY) – Not Appalachian; a dome of ancient rock uplifted recently (geologically).

Ozarks (MO/AR), Ouachitas (AR/OK) – Interior highlands, distinct from Appalachians.

Why the Disparity?

Western North America sits on an active plate boundary (subduction, transform, extension). Eastern North America is on the stable interior (craton) of the plate—no mountain-building forces for 200+ million years. The Appalachians are fossils of past collisions (Taconic, Acadian, Alleghenian orogenies).

Result: The West has young, high, rugged, seismically active mountains. The East has old, low, rounded, stable highlands. Both beautiful—geologically, they're different planets.