Table 3.

NCHS urban–rural classification scheme for counties

Urbanization level	Classification rule
Metropolitan counties
Large central metro	Populations of 1 million or more that
	1. Contain the entire population of the largest principal city, or
	2. Have their entire population contained in the largest principal city, or
	3. Contain at least 250,000 inhabitants of any principal city
Large fringe metro	Populations of 1 million or more that did not qualify as large central metro counties
Medium metro	Populations of 250,000–999, 999
Small metro	Populations of 50,000–250,000
Non-metropolitan counties
Micropolitan	Populations of 10,000–49,999
Noncore	Populations less than 10,000