Manhattan is the most densely populated of the five boroughs of New York City. The borough is coterminous with New York County, founded on November 1, 1683 as an original county of the U.S. state of New York. The borough consists mostly of Manhattan Island, bounded by the East, Hudson, and Harlem Rivers, but also includes several small adjacent islands, as well as Marble Hill, a small neighborhood on the U.S. mainland. Manhattan is often said to be the economic and cultural center of the United States and serves as home to the United Nations Headquarters. Wall Street, in Lower Manhattan, has been called the financial capital of the world, and is home to the New York Stock Exchange and NASDAQ. Many multinational media conglomerates are based in the borough. Historically documented to have been purchased by Dutch colonists from Native Americans in 1626 for the equivalent of US$24, Manhattan real estate has since become among the most expensive in the world, with the value of Manhattan Island, including real estate, estimated to exceed US$3 trillion in 2013. New York County is the most densely populated county in the United States, and is more dense than any individual American city. It is one of the most densely populated areas in the world, with a Census-estimated 2013 population of 1,626,159 living in a land area of , or 71,229 residents per square mile (27,502/km²). On business days, the influx of commuters increases that number to over 3.9 million, or more than 170,000 people per square mile. Manhattan has the third-largest population of New York’s five boroughs, after Brooklyn and Queens, and is the smallest borough in terms of land area. Many districts and landmarks in Manhattan have become well known to New York City’s approximately 50 million annual visitors. Times Square, iconified as “The Crossroads of the World” and “The Center of the Universe”, is the brightly illuminated hub of the Broadway Theater District, one of the world’s busiest pedestrian intersections, and a major center of the world’s entertainment industry. The borough hosts many world-renowned bridges, skyscrapers, and parks. Manhattan’s Chinatown incorporates the highest concentration of Chinese people in the Western Hemisphere. The Stonewall Inn in Greenwich Village is considered the birthplace of the modern gay rights movement. Numerous colleges and universities are located in Manhattan, including Columbia University, New York University, and Rockefeller University, which have been ranked among the top 35 in the world. The city of New York was founded at the southern tip of Manhattan, and the borough houses New York City Hall, the seat of city government and a National Historic Landmark that is listed on the National Register of Historic Places.