They are part of the Cascade Volcanic Arc , a segment of the Cascade Range in western North America extending from southern British Columbia through Washington and Oregon to Northern California .
The Three Sisters are volcanic peaks that form a complex volcano in the U.S. state of Oregon .
Three Sisters are part of the Cascade Volcanic Arc , a segment of the Cascade Range in western North America extending from southern British Columbia through Washington and Oregon to Northern California .
The Three Sisters are volcanic peaks that form a complex volcano in the U.S. state of Oregon .