Percent Rural and Urban Population by Counties

The only county data on rural status I know is USDA typology (though not-rural is not the same as urban) 

https://www.ers.usda.gov/topics/rural-economy-population/rural-classifications/
https://www.ers.usda.gov/data-products/rural-urban-continuum-codes/

there’s also Rural Urban Continuum codes above for counties which might help with the Urban part ( and also make some distinctions within rural counties) 

—Tim Henderson 

The only county data on rural status I know is USDA typology (though not-rural is not the same as urban) 

https://www.ers.usda.gov/topics/rural-economy-population/rural-classifications/
https://www.ers.usda.gov/data-products/rural-urban-continuum-codes/

there’s also Rural Urban Continuum codes above for counties which might help with the Urban part ( and also make some distinctions within rural counties) 

—Tim Henderson 

That ain't the half of it, Tim. Don't forget RUCAs, FORHP classifications, USDA Urban Influence Codes, Isserman Rural-Urban Density Codes, or any of the other two dozen or so rural definitions in use at various federal agencies.

just to state the obvious:

USDA/ERS's rural-urban continuum and these others are methodologically independent of USCB's urban-rural designations. But interesting. So... shop around for the classification scheme that fits your purpose. 

--TG

Right you are, Todd. I was responding more to Tim than to Neel_2019.

Todd Graham said:

shop around

Indeed, this is what I tell our clients & users:

• Learn what urban/rural classification system predominates in your area of research.
• Determine what geographic level(s) are available in your source data.
• Choose geographic granularity based on scope or type of analysis.

Even though it hasn't been updated since 2013, I really like the CDC's urban-rural classification system for counties:

www.cdc.gov/.../urban_rural.htm

Ooh, I like it! And it looks like they will be updating it this year.

Dept of Education urban/rural 12 category (4 major with 3 minor in each major) GIS layer -- https://nces.ed.gov/programs/edge/Geographic/LocaleBoundaries Todd Graham Tim Henderson

and "Census-defined" -- very interesting, Thanks Stas. At a glance looks like they're based on ZCTA so they can match school locations? This may be the first public data I've seen that attempts to define "suburban" -- some places have been doing that with aerial photography  (NY Times) or other data tricks (Brookings)