A name can refer to several geographic units
A city proper is a legally defined incorporated place. A county or county equivalent is a separate geographic unit that can contain incorporated places and other residents. A metropolitan statistical area is an official statistical grouping of counties. A familiar city name in a metro title does not make the metro total the population of that city.
A city can extend into more than one county. Likewise, a metropolitan area can span several states. A whole-city population should not be labeled as the population inside each associated county, and a whole-metro total should not be presented as entirely residing in every associated state.
Whole-place and place-part records
The Census subcounty estimates file distinguishes incorporated places from county/place parts and minor civil divisions. This publication uses SUMLEV 162 whole incorporated-place records for city profiles. SUMLEV 157 identifies the portion of a place inside a county and supports the geographic relationship table. It is not ranked as an additional city.
Consolidated governments require further care. A consolidated-city total and a balance record can describe different populations. A balance excludes separately incorporated places as defined by the source. Balance profiles are labeled here and excluded from ordinary-place rankings; their totals are not substituted for a full consolidated government.
Why adding places can be misleading
Summing incorporated city totals does not normally reproduce a county total. Some county residents live outside incorporated places; some listed whole cities cross the county boundary. County subdivisions, incorporated places and census-designated places can overlap as geographic categories. Adding them without a nonoverlapping relationship model double-counts residents.
A custom region should begin with whole, nonoverlapping counties from one release and retain the member list. Recompute a share from summed numerators and denominators rather than averaging percentages. Density must use summed compatible land area. Medians cannot generally be averaged to create a valid regional median.
Choosing the right unit
Use the unit the research question asks about. For a municipal resident total, choose the incorporated place. For a county service area, choose the county equivalent. For a labor-market statistical region, use its official metro definition and delineation date, not an informal collection of nearby cities. An urban area is another separate geographic definition and is not interchangeable with a metro.
The launch registry supports nation, states/DC, county equivalents and eligible incorporated places. Metro profiles remain outside launch coverage pending validation. Read the Census geographic definitions and subcounty file layout. Compare like units with the population comparison tool.