Castle Clinton (also known as Fort Clinton and Castle Garden) is a circular sandstone fort within Battery Park at the southern end of Manhattan in New York City. Built from 1808 to 1811, it was the first American immigration station, predating Ellis Island. More than 7.5 million people arrived in the United States at Fort Clinton between 1855 to 1890. Over its active life, it has also functioned as a beer garden, exhibition hall, theater, and public aquarium. The structure is a New York City designated landmark and a United States national monument, and it is listed on the National Register of Historic Places.