Manhattan (coterminous with New York County) is one of the five boroughs of New York City. With a 2007 population of 1,620,867 living in a land area of 22.96 square miles (59.47 km²), it is the most densely populated county in the United States at 70,595 residents per square mile (27,267/km²). It is also one of the wealthiest counties in the United States, with a 2005 personal per capita income above $100,000. The borough consists of Manhattan Island, Roosevelt Island, Randalls Island, almost one-tenth of Ellis Island, the above-water portion of Liberty Island, several much smaller islands, and a small section on the mainland of New York State adjacent to the Bronx.
Manhattan is a major commercial, financial, and cultural center of the United States and the world. Most major radio, television, and telecommunications companies in the United States are based here, as well as many news, magazine, book, and other media publishers. Manhattan has many famous landmarks, tourist attractions, museums, and universities. It is also home to the headquarters of the United Nations. Manhattan has the largest central business district in the United States, is the site of both the New York Stock Exchange and NASDAQ, and is the home to the largest number of corporate headquarters in the nation. It is indisputably the center of New York City and the New York metropolitan region, holding the seat of city government, and the largest fraction of employment, business, and recreational activities.
The name Manhattan derives from the word Manna-hata, as written in the 1609 logbook of Robert Juet, an officer on Henry Hudson's yacht Halve Maen (Half Moon). A 1610 map depicts the name Manahata twice, on both the west and east sides of the Mauritius River (later named the Hudson River). The word "Manhattan" has been translated as "island of many hills" from the Lenape language. The Encyclopedia of New York City offers other derivations, including from the Munsee dialect of Lenape: manahachtanienk ("place of general inebriation"), manahatouh ("place where timber is procured for bows and arrows"), or menatay ("island").
Manhattan Island is bounded by the Hudson River to the west and the East River to the east. To the north, the Harlem River divides Manhattan from The Bronx and the mainland United States. Several small islands are also part of the borough of Manhattan, including Randall's Island, Ward's Island, and Roosevelt Island in the East River, and Governors Island and Liberty Island to the south in New York Harbor. Manhattan Island is 22.7 square miles (58.8 km²) in area, 13.4 miles (21.6 km) long and 2.3 miles (3.7 km) wide, at its widest (near 14th Street). New York County as a whole covers a total area of 33.77 square miles (87.46 km²), of which 22.96 square miles (59.47 km²) are land and 10.81 square miles (28.00 km²) are water.
One Manhattan neighborhood is actually contiguous with The Bronx. Marble Hill at one time was part of Manhattan Island, but the Harlem River Ship Canal, dug in 1895 to improve navigation on the Harlem River, separated it from the remainder of Manhattan as an island between the Bronx and the remainder of Manhattan. Before World War I, the section of the original Harlem River channel separating Marble Hill from The Bronx was filled in, and Marble Hill became part of the mainland.
Marble Hill is one example of how Manhattan's land has been considerably altered by human intervention. The borough has seen substantial land reclamation along its waterfronts since Dutch colonial times, and much of the natural variation in topography has been evened out.
Early in the nineteenth century, landfill was used to expand Lower Manhattan from the natural Hudson shoreline at Greenwich Street to West Street. When building the World Trade Center, 1.2 million cubic yards (917,000 m³) of material was excavated from the site. Rather than dumping the spoil at sea or in landfills, the fill material was used to expand the Manhattan shoreline across West Street, creating Battery Park City. The result was a 700 foot (210 m) extension into the river, running six blocks or 1,484 feet (450 m), covering 92 acres (37 ha), providing a 1.2 mile (1.9 km) riverfront esplanade and over 30 acres (12 ha) of parks.
Manhattan is loosely divided into downtown, Midtown, and uptown, with Fifth Avenue dividing Manhattan's east and west sides.
Manhattan has fixed vehicular connections with New Jersey to the west via the George Washington Bridge, Holland Tunnel and Lincoln Tunnel, and to three of the four other New York City boroughs—the Bronx to the northeast and Brooklyn and Queens on Long Island to the east and south. Its only direct connection with the fifth New York City borough is the Staten Island Ferry across New York Harbor, which is free of charge. The ferry terminal is located adjacent to Battery Park at its southern tip. It is possible to travel to Staten Island via Brooklyn, using the Verrazano-Narrows Bridge.
The Commissioners' Plan of 1811, called for twelve numbered avenues running north and south roughly parallel to the shore of the Hudson River, each 100 feet (30 m) wide, with First Avenue on the east side and Twelfth Avenue in the west. There are several intermittent avenues east of First Avenue, including four additional lettered avenues running from Avenue A eastward to Avenue D in an area now known as Alphabet City in Manhattan's East Village. The numbered streets in Manhattan run east-west, and are 60 feet (18 m) wide, with about 200 feet (61 m) between each pair of streets. With each combined street and block adding up to about 260 feet (79 m), there are almost exactly 20 blocks per mile. Fifteen crosstown streets were designated as 100 feet (30 m) wide, including 34th, 42nd, 57th and 125th Streets, some of the borough's most significant transportation and shopping venues. Broadway is the most notable of many exceptions to the grid, starting at Bowling Green in Lower Manhattan and continuing north into the Bronx at Manhattan's northern tip. In much of Midtown Manhattan, Broadway runs at a diagonal to the grid, creating major named intersections at Union Square, Herald Square (Sixth Avenue and 34th Street), Times Square (Seventh Avenue and 42nd Street), Columbus Circle (Eighth Avenue/Central Park West and 59th Street)
A consequence of the strict grid plan of most of Manhattan, and the grid's skew of approximately 28.9 degrees, is a phenomenon sometimes referred to as Manhattanhenge (by analogy with Stonehenge). On separate occasions in late May and early July, the sunset is aligned with the street grid lines, with the result that the sun is visible at or near the western horizon from street level. A similar phenomenon occurs with the sunrise in January and December.
The Wildlife Conservation Society, which operates the zoos and aquariums in the city, is currently undertaking The Mannahatta Project, a computer simulation to visually reconstruct the ecology and geography of Manhattan when Henry Hudson first sailed by in 1609, and compare it to what we know of the island today.
Manhattan is the home and location of the main characters and where the majority of the film takes place. During the night of the monster's arrival, the U.S. military and the National Guard was mobilized into Manhattan and made attempts to stop the creature, but their weapons were completely ineffective.
At 0442 (4:42 AM), the United States government approved the execution of the HAMMER-DOWN Protocol on Manhattan, in a last ditch effort to destroy the Large Scale Aggressor and the Human Sized Parasites. 120 minutes later, at 1842 (6: 42 AM) hours, the HAMMER-DOWN Protocol was initiated, and U.S. military aircraft flew over Manhattan, deploying their payloads and bombing the creature. 
- Manhattan on Wikipedia