Manhattan is one of the boroughs of New York City. Located primarily on Manhattan Island at the mouth of the Hudson River, the boundaries of the borough are identical to those of New York County, an original county of the state of New York. It consists of Manhattan Island and several small adjacent islands: Roosevelt Island, Randall's Island, Ward's Island, Governors Island, Liberty Island, part of Ellis Island, and U Thant Island; as well as Marble Hill, a small section on the mainland near the Bronx. The original city of New York began at the southern end of Manhattan, and expanded in 1898 to include surrounding counties. It is the smallest yet most urbanized of the five boroughs.
Manhattan is a major commercial, financial, and cultural center of both the United States and the world. Many major radio, television, and telecommunications companies in the United States are based here, as well as many news, magazine, book, and other media publishers. Manhattan has many famous landmarks, tourist attractions, museums, and universities. It is also home to the headquarters of the United Nations. Manhattan has the largest central business district in the United States, is the site of both the New York Stock Exchange and NASDAQ, and is the home to the largest number of corporate headquarters in the country. It is the center of New York City and the New York metropolitan region, hosting the seat of city government and a large portion of the area's employment, business, and entertainment activities. As a result, residents of New York City's other boroughs such as Brooklyn and Queens often refer to a trip to Manhattan as "going to the city".