Context: 155th Street is a major crosstown street considered to form the boundary between Harlem and Washington Heights. It is the northernmost of the 155 crosstown streets mapped out in the Commissioner's Plan of 1811 that established the numbered street grid in Manhattan.

Question: How many crosstown streets are mapped in the Commissioner's Plan of 1811?
Answer: 155

Question: Which street is the northernmost of the streets mapped in the Commissioner's Plan of 1811?
Answer: 155th Street

Question: Which street forms the boundary between Harlem and Washington Heights?
Answer: 155th Street

Question: What document established Manhattan's numbered street grid?
Answer: Commissioner's Plan of 1811

Question: 155th Street forms the boundary between Harlem and what other neighborhood?
Answer: Washington Heights