Claim: Marble Hill, Manhattan is not an island.

Marble Hill is the northernmost neighborhood in the New York City borough of Manhattan . It is the only Manhattan neighborhood on the mainland of North America . Marble Hill was occupied as a Dutch colonial settlement in 1646 , and gained its current name in 1891 because of marble deposits underneath the neighborhood .   Politically a part of Manhattan and New York County , Marble Hill became an island in the Harlem River when it was separated from the island of Manhattan by the construction of the Harlem Ship Canal in 1895 . In 1914 , the Harlem River was filled in on the north side of Marble Hill , connecting it to the North American mainland and the Bronx . Because of this change in geography , Marble Hill is often associated with the Bronx and is part of two of the latter 's Community Board Districts .