Oregon (locally pronounced "OR-uh-gun") is a state located in the western United States bordering the Pacific Ocean, California, Washington, Idaho, and Nevada. Its northern border lies along the Columbia River and the east along the Snake River. Two north-south mountain ranges - the Coastal Range and the Cascade Mountain Range - form the two boundaries of the Willamette Valley, one of the most fertile and agriculturally productive regions in the world. Oregon is known for its abundant rainfall, but only the western half of the state is notably rainy; east of the Cascades the climate is much more arid.