I would suggest Calvert has become largely exurban; not (yet) sufficiently developed to be considered suburban, while rapidly shedding its agricultural economy and rural culture. Same applies to most of SoMD.
ex·urb /ˈɛksərb, ˈɛgzərb/ Pronunciation Key - Show Spelled Pronunciation[ek-serb, eg-zerb] Pronunciation Key - Show IPA Pronunciation
–noun
a small, usually prosperous, community situated beyond the suburbs of a city.
[Origin: 1950–55, Americanism; ex-1 + (sub)urb]
Dictionary.com Unabridged (v 1.1)
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2006.