Santa Clara County, California, officially the County of Santa Clara, is a county in the U.S. state of California. As of the 2010 census, the population was 1,781,642. The county seat and largest city is San Jose, the tenth-most populous city in the United States. Santa Clara County is part of the San Jose-Sunnyvale-Santa Clara, CA Metropolitan Statistical Area as well as the San Jose-San Francisco-Oakland, CA Combined Statistical Area. Located at the southern end of the San Francisco Bay, the highly urbanized Santa Clara Valley within Santa Clara County is also known as Silicon Valley. Santa Clara is the most populous county in the San Francisco Bay Area and in Northern California, and is one of the most affluent counties in the United States.