Castle Clinton or Fort Clinton, once known as Castle Garden, is a circular sandstone fort now located in Battery Park at the southern tip of Manhattan Island, New York City, in the United States. It is perhaps best remembered as America's first immigration station (predating Ellis Island), where more than 8 million people arrived in the U.S. from 1855 to 1890. Over its active life, it has also functioned as a beer garden, exhibition hall, theater, public aquarium, and finally today as a national monument.