Castle Clinton National Monument - http://www.nps.gov/cacl

More than a dozen forts were built to defend New York Harbor at the time of the War of 1812. The Southwest Battery was constructed on the rocks off the tip of Manhattan Island between 1808 and 1811. Although fully armed, the fort never had occasion to fire upon an enemy. In 1817, the fort was renamed Castle Clinton in honor of DeWitt Clinton, Mayor and later Governor of New York. The army vacated the fort in 1821 and the structure was deeded to New York City in 1823. In the summer of 1824, a new restaurant and entertainment center opened at the site, then called Castle Garden. A roof was added in the 1840s and Castle Garden served as an opera house and theater until 1854. The "Swedish Nightengale" Jenny Lind made her American debut here in 1850.