This is related to an earlier question (Understanding U.S. Census MSA to place relationships?), on which I'm still unclear. Can MSAs (CBSAs) split counties?

According to Glaeser et al. (Growth in Cities, 1992, p1135), in 1956:

In some cases, an SMA* contains several counties; in others (only in New England), several SMAs split a single county.

*SMAs were MSAs of the time, and Glaeser et al. compare 1956 SMAs with 1987 MSAs.

But as of the latest U.S. census delineation file, I count (perhaps mistakenly) not more than one CBSA (Metro- or Micro-politan Area) per county, even in New England. This conforms with what the U.S. Census says, that "Counties or equivalent entities form the geographic 'building blocks' for metropolitan and micropolitan statistical areas throughout the United States and Puerto Rico." This could be because the U.S. Census's methodology has evolved on that score since 1956. For example, the latest methodology could prevent splitting counties by assigning ambiguous counties entirely to the 'dominant' CBSA (dominant in terms of commuting patterns).

Is it theoretically possible for contiguous CBSAs to split a county (especially an 'outlying county', per U.S. Census terminology)? This would also imply that contiguous CBSAs are possible.

  • This appears to be a series of questions that I suspect may be just as or more on-topic at the Open Data Stack Exchange.
    – PolyGeo
    Commented Apr 7, 2017 at 23:48
  • @syre did you ever come to a conclusion on this? was about to ask the same question and had your exact same logic.
    – user128912
    Commented Feb 10, 2020 at 15:48

1 Answer 1


MSAs are defined in terms of entire counties, even in New England.* Counties cannot belong to multiple MSAs at the same time.

The definition of MSAs changes over time, so it is theoretically possible that a county could switch from one to another, but I haven't checked. I also haven't checked whether any MSAs are contiguous.

Incidentally, most MSAs are small and comprise a single county.

*EDIT: I guess the Census Bureau must have harmonised New England MSA definitions with the rest of the country since Glaeser's research sample dates, but I can't point to a reference about that change.

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