It looks to me as if the US Department of Education employs just the
type of classification/definition you are looking for, dividing
populated areas up into eight neat categorizations:
Locale Code (School): The Locale Code defines how the school is
situated in a particular location relative to 1990 Census populous
areas, based on the school's location address. No Locale Codes have
been assigned to the outlying areas. The Code translations are as
Locale Code Locale Type Definition
1 Large Central City -- Central city of a Metropolitan Statistical
Area (MSA) with a population greater than or equal to 250,000.
2 Mid-size Central City -- Central City of an MSA with a population
less than 250,000.
3 Urban Fringe of Large City -- Place within an MSA of a Large Central
City and defined as urban by the Census Bureau.
4 Urban Fringe of Mid-Size City -- Place within an MSA of a Mid-size
Central City and defined as urban by the Census Bureau.
5 Large Town -- Town not within an MSA, with a population greater than
or equal to 25,000.
6 Small Town -- Town not within an MSA and with a population less than
25,000 and greater than or equal to 2,500 people.
7 Rural, outside MSA -- A place with less than 2,500 people and coded
rural and outside an MSA by the Census Bureau.
8 Rural, inside MSA -- A place with less than 2,500 people and coded
rural and inside an MSA by the Census Bureau.
You can find this list by heading to the "Public School Districts"
search page at the Department of Education website:
and near the top of the page, clicking on the link that says: "About
the Data", and then clicking within the text that opens up on the link
that says: "Glossary".
Scrolling down the Glossary list to the "Locale Code" will take you
the text I excerpted above.
You can see formal reference to this same list at a recent Federal Register notice:
DEPARTMENT OF EDUCATION
Safe Schools/Healthy Students
AGENCY: Office of Safe and Drug-Free Schools, Department of Education.
ACTION: Notice of proposed priority, selection criteria, requirements,
Beginning on page 12845 of this notice, they provide definitions for
the various levels of urbanization.
I hope this meets your needs.
Before rating this answer, please let me know if you need any
additional information, and I'll be happy to assist you further.
search strategy: To tell the truth, I was searching on an entirely
different topic, stumbled across a reference to "Urban Fringe"
categories, and remembered your question. A happy confluence of