This historic site in New York City was built in 1811 as one of ﬁve forts to defend New York Harbor. It never saw any military action and was eventually given to New York City in 1823. Between 1824 and 1854, it served as a promenade, beer garden, exhibition hall, opera house, and theater before becoming the U.S.’s ﬁrst immigration station in 1855. Over the next 35 years, 8 million people went through Castle Clinton before the government took control of immigration processing in and moved it to Ellis Island. From 1896 to 1941, the castle took on another face as the New York City Aquarium, one of the city’s most popular attractions. In the years since, there were many moments where the castle was almost demolished, but luckily it has been saved and today appears much as it did in its earliest years.