California is a state in the Western United States. California borders Oregon to the north, Nevada and Arizona to the east, and the Mexican state of Baja California to the south. With over 39.5 million residents across a total area of approximately 163,696 square miles, it is the most populous and the third-largest U.S. state by area. It is also the most populated subnational entity in North America and the 34th most populous in the world.