The Bay Area is the term generally used to describe San Francisco peninsula, and the large outcropping of associated suburban communities. According to the Metropolitan Transportation Commission's website, the Bay Area is a roughly 7,000-square-mile area with an estimated 7 million residents who live in the following nine counties:

• San Francisco
• Alameda
• Contra Costa
• Marin
• Napa
• San Mateo
• Santa Clara
• Solano
• Sonoma

The East Bay is often used and understood to refer to Alameda County and Contra Costa County encompassing Fremont to Oakland to Richmond.