Savannah's architecture, history, and reputation for Southern charm and hospitality are internationally known. The city's former promotional name was "Hostess City of the South," a phrase still used by the city government. An earlier nickname was "the Forest City", in reference to the large population and species of oak trees that flourish in the Savannah area. These trees were especially valuable in shipbuilding during the 19th century. In 2014, Savannah attracted 13.5 million visitors from across the country and around the world. Savannah's downtown area is one of the largest National Historic Landmark Districts in the United States.