The US government's official designation for neighborhoods is measured by a something called a census tract.
Census tracts are small, relatively permanent subdivisions of a county that are defined by the U.S. Census Bureau with the help of local authorities. Each tract is bounded to contain areas with homogeneous population characteristics such as economic status, lifestyle, and living conditions.
Census tracts usually have 4,000 persons, but can range between 1,500 and 8,000 persons. This is the most fine-grained area for which detailed information is made available from the government, to protect the individual privacy of each of us. Because census tracts are based on population, they vary in size depending on the density of settlement. In urban areas, they are small, and in rural areas they can cover an entire small town or even a few small towns in very rural areas.
Sometimes Census tracts do not have a name, and they get referred to by the most prominent intersection within the boundaries of the tract. Historic areas and densely populated tracts usually have proper names, which we commonly referred to as the Neighborhood.