The New York Times has a great article and series of maps looking at what people call a given block and neighborhood.

The work presents neighborhoods with clear boundaries and fuzzy ones. It also looks at what boundaries exist with varying degrees of consensus:

The article drills down into the age-old UES vs East Harlem boundary issue. The first map of the area is this:

with a border shifting upward from 96th Street. At the same time, a more detailed view notes that Street Easy claims that the thin line of buildings fronting on Central Park, are part of the UES:

Fortunately, we have the unwavering voice of Xavier Santiago, the Chair of Community Board 11, who unequivocally stated:

As Seen In Harlem

Madison/120