Manhattan is the most densely populated and the oldest of the
five boroughs of
New York City. Located primarily on the island of Manhattan at the mouth of the
Hudson River, the boundaries of the borough are identical to those of
New York County, an original county of the
U.S. state of
New York. The borough and county consist of Manhattan Island and
several small adjacent islands:
Roosevelt Island,
Randall's Island,
Wards Island,
Governors Island,
Liberty Island, part of
Ellis Island,
Mill Rock, and
U Thant Island; as well as
Marble Hill, a very small area on the mainland bordering
the Bronx. The original city of New York began at the southern end of Manhattan, expanded northward, and then between 1874 and 1898, annexed land from surrounding counties.