Final answer:
The classification of a county as metro or non-metropolitan is determined by the U.S. Census Bureau based on population size, urban core areas, commuting patterns, urban uses, and population density.
Step-by-step explanation:
A county can be classified as metro (metropolitan) or non-metropolitan based on several criteria developed by the United States Census Bureau. For a county to be considered metropolitan, it generally must have an urban core area with a population of 50,000 or more. If a smaller city within a county has between 10,000 and 50,000 residents and is a focal point for commuting in the surrounding region, it may be designated as a Micropolitan Statistical Area (μSA), which is a type of non-metropolitan area.
Further complications arise when considering the various terms used to describe human settlements, ranging from hamlets and villages to towns and cities. In the U.S., the Census Bureau uses the terms 'rural' and 'urban' to distinguish non-city regions from cities, with updates to this classification system helping to define metro and non-metropolitan areas more precisely. An area's classification as 'urban' can also be affected by non-residential uses such as factories and airports, and population density plays a key role, as regions with a density of at least 500 persons per square mile near an urban area are included in that urban classification.