The ocean that borders the west coast of North America is the Pacific Ocean. It is the largest ocean on Earth, covering more area than all the landmasses combined. The Pacific Ocean is known for its significant role in global climate patterns, particularly through phenomena like El Niño and La Niña. Additionally, it is home to diverse marine ecosystems and serves as a vital shipping route. Coastal cities such as San Francisco and Vancouver thrive due to their location on the Pacific, making it crucial for trade and tourism.