The Pacific Northwest (PNW), sometimes referred to as Cascadia, is a geographic region in western North America bounded by the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though no official boundary exists, the most common conception includes the U.S. states of Oregon, Washington, and Idaho and the Canadian province of British Columbia. Some broader conceptions reach north into Alaska and the Yukon and south into northern California. Other conceptions may be limited to the coastal areas west of the Cascade and Coast mountains. The variety of definitions can be attributed to partially overlapping commonalities of the region's history, culture, geography, society, and other factors.