One thing I just recalled is that if you maintain a small exceptions lookup table (i.e. the ones that span state boundaries), you can use ZIP Codes as a way to uniquely look up a county name.

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graywh 3 days ago | parent | next [-]

ZIP codes also span county boundaries that aren't state boundaries -- I know of several in my county alone

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mulmen 3 days ago | parent | prev [-]

Why would you do this?

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paulsmith 3 days ago | parent [-]

For example, health care plans in the US are county-specific with regard to premiums, co-pays, etc. (based on demographics). Allowing someone to type in their ZIP Code to get started can be a better user experience than having them pick their county.

https://www.healthcare.gov/see-plans/

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mulmen 3 days ago | parent [-]

Except when it isn’t. I’d be curious to know the population in areas where a zip code spans multiple counties.

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paulsmith 3 days ago | parent [-]

In that case, each county that corresponds to that ZIP Code is shown and the user can disambiguate manually.

	▲	mulmen 3 days ago \| parent [-]
		Yeah it makes it easier. And I’m appreciative of the idea of making address entry easier for users but if they have to disambiguate did you actually make it easier? I think Zillow does it best. You just type your address in a box and it looks up the normalized full address. That makes everyone happy.