From Wikipedia:
Upper Manhattan denotes the more northerly region of the New York City Borough of Manhattan. Its southern boundary may be defined anywhere between 59th Street and 155th Street. Between these two extremes lies the most common definitions of Upper Manhattan as Manhattan above 96th Street (the southern boundary of Manhattan Valley in the west and Spanish Harlem in the east) . This definition of Upper Manhattan takes in the neighborhoods of Marble Hill, Inwood, Washington Heights (including Fort George, Sherman Creek and Hudson Heights), Harlem (including Sugar Hill and Hamilton Heights), and parts of the Upper West Side (Morningside Heights and Manhattan Valley).
In the late 19th century, the IRT Ninth Avenue Line and other elevated railroads brought urban sprawl to the previously rustic Upper Manhattan. Until the late 20th century it was less influenced by the gentrification that had taken place in other parts of New York over the previous 30 years.
Like other residential areas, Upper Manhattan is not a major center of tourism in New York City, although some tourist attractions, such as The Cloisters lie within it. Tourist maps similarly pay scant attention to the boroughs of the Bronx, Brooklyn, Queens, and Staten Island. Even many native New Yorkers tend to treat Upper Manhattan like another borough, its distance from Midtown Manhattan and comparatively lower rents leading many to exclude this northern neck from the area New Yorkers call "The City".
The Upper West Side is more affluent than its northern neighbors such as Manhattanville, Morningside Heights, Inwood, etc. The Upper East side is similarly more affluent than its northern neighbor Spanish Harlem. Thus the 96th street definition comes from the East Side as well. Gentrification not yet completed in some neighborhoods, crime, graffiti, etc., are associated with Upper Manhattan.[2] Gentrification is occurring at a different pace, rate, and style than Soho, East Village, etc., due to different demographics.
All of Upper Manhattan is contained in the larger area New Yorkers know as Uptown (above 59th Street). The Bronx, though not in Manhattan, is often colloquially referred to as "Uptown", especially in the context of hip hop/inner-city culture.
Many diplomatic missions are located in former mansions on the Upper East Side.
