Shishim Ribo in New York City and Brooklyn
New York and Brooklyn are not small isolated towns. Rav Moshe's responsa analyze their population and public routes as parts of a large connected city.
The city around the neighborhood
Major roads and continuous public movement connect Brooklyn neighborhoods to one another and to the rest of New York. People cross local boundaries for work, school, shopping, shul, and transit without passing a physical wall or gate.
A perimeter drawn around one community therefore does not necessarily reduce the public-domain question to the residents inside it. The roads may serve a much larger citywide public.
Rav Moshe's New York analysis
Igros Moshe Orach Chaim I:138–139 lays out Rav Moshe's early discussion of Manhattan and large-city public domains. IV:87–89 addresses later Manhattan and Flatbush questions, and V:28 returns to Brooklyn and public practice.
Across these teshuvos, Rav Moshe resists treating a small neighborhood as though it were detached from New York. Population and the roads serving the larger city remain part of the analysis.
Crown Heights within Brooklyn
Crown Heights lies within the same connected borough and road system. Eastern Parkway, major avenues, local streets, transit, and traffic link it to the population beyond any proposed eruv line.
The neighborhood Beis Din gives the direct practical ruling. Rav Moshe's responsa explain the large-city background that the local Rabbonim cite.