San Francisco, officially the City and County of San Francisco, is the cultural, commercial, and financial center of Northern California and the only consolidated city-county in California. San Francisco encompasses a land area of about 46.9 square miles (121 km²) on the northern end of the San Francisco Peninsula, which makes it the smallest county in the state. It has a density of about 18,187 people per square mile (7,022 people per km²), making it the most densely settled large city (population greater than 200,000) in the state of California and the second-most densely populated major city in the United States after New York City. San Francisco is the fourth-most populous city in California, after Los Angeles, San Diego and San Jose, and the 13th-most populous city in the United States—with a Census-estimated 2014 population of 852,469. The city and its surrounding areas are known as the San Francisco Bay Area, which is a part of the larger OMB designated San Jose-San Francisco-Oakland combined statistical area, the fifth most populous in the nation with an estimated population of 8.6 million.
Although the Financial District, Union Square, and Fisherman's Wharf are well-known around the world, San Francisco is also characterized by its numerous culturally rich streetscapes featuring mixed-use neighborhoods anchored around central commercial corridors to which residents and visitors alike can walk. Because of these characteristics, San Francisco is ranked the second "most walkable" city in the U.S. by Walkscore.com. Many neighborhoods feature a mix of businesses, restaurants and venues that cater to both the daily needs of local residents while also serving many visitors and tourists. Some neighborhoods are dotted with boutiques, cafes and nightlife such as Union Street in Cow Hollow, 24th Street in Noe Valley, Valencia Street in the Mission, Grant St. in North Beach, and Irving Street in the Inner Sunset. This approach especially has influenced the continuing South of Market neighborhood redevelopment with businesses and neighborhood services rising alongside high-rise residences.