"Though the neighborhood was once considered to run as far south as 133rd Street, modern usage defines the neighborhood as running north from Hamilton Heights at 155th Street to Inwood, topping out at just below Hillside Avenue or Dyckman Street, depending on the source." Wiki
Come see old photos of some of those streets here: Old NYC
My wife's great-great-grandmother whose parents were from Germany lived on W. 146th St. Here's what it looks like today (from Google)
And here's what it looked like sometime before that (don't know exact date of photo)
The red building is the same but in the old photograph there's no building to the right. Today there is a building attached to it.