SmartyStreets

How to Find a County by ZIP Code, City or Address Lookup

Every mailing address is located within a specific county AND a specific ZIP Code. Therefore, if you know what the ZIP Code or city for a specific address, you can find out what county that address is located in. All you need is an address validation service provider. Here is a simple example of how to lookup a county using a ZIP Code. We'll also look at an example of how to perform a county lookup using a mailing address.

Before you embark on your journey, there is something you need to know. Cities and ZIP Codes frequently cross county and even state lines. Some cities cross into five different counties and as many as 20% of the ZIP Codes cross county lines. This means that if you enter a city or ZIP Code into our tool, it may return information for more than one county.

Conversely, a single address will only ever be located in one county. So, for the most precise results, use the full address to find county information rather than the city or ZIP Code.

Find county by ZIP Code step 1 - Visit single address demo page

Table of contents:

How to Use a ZIP Code to Find a County

Step 1. Go to the website of an address validation services provider of your choice. In this example, we'll find a ZIP Code's corresponding county designation using the SmartyStreets' address validation demo.

Find county by ZIP Code step 1 - Visit single address demo page

Step 2. Look for "Step 2: Choose a lookup type" and choose "city/state or ZIP Code" from the dropdown menu.

Find county by ZIP Code step 2 - Choose city/state or ZIP Code

Step 3. Enter the ZIP Code in the "ZIP Code" form field of "Step 3"

Find county by ZIP Code step 3 - Enter ZIP Code in form field

Step 4. Click on "View Results"

Step 5. In the "Output Fields" section of the results, look for "County Name". There you will see the county associated with the ZIP Code you entered.

Find county by zip code step 5 - Look for 'County Name' in the 'Output Fields' section

You can also find county info using this method by submitting the name of a city instead of a ZIP Code. On "Step 3", simply enter the city name instead of the ZIP Code.

Alternate method: On step 3 enter city and state to find county info instead of ZIP Code

How to Find A County Using a Mailing Address

The process for finding a county by using a mailing address is very similar to finding a county using a ZIP Code. However, it is not necessary to have the ZIP Code for this process. You can use a mailing address to find a county by using the following steps:

Step 1. Go to the website of an address validation service provider of your choice. For this example, we'll again use the SmartyStreets' address validation demo for Single Addresses.

County lookup by address step 1 - Visit single address validation demo page

Step 2. Look for "Step 2: Choose a lookup type" and choose "address components" from the dropdown menu.

County lookup by address step 2 - Select address components from dropdown

Step 3. Enter the address info into the respective form fields of "Step 3". You can enter a ZIP Code into the "ZIP Code" field if you want to, but it is not necessary.

County lookup by address step 3 - Enter the street address components

Step 4. Click on "View Results"

Step 5. In the "Metadata" section of the results, look for "County Name". There you will see the county associated with the address that you entered.

County lookup by address step 5 - Look for 'County Name' in the 'Metadata' section

Programmatically Finding County Data by Using a ZIP Code API

Sometimes, you need to find A LOT of county names for A LOT of different ZIP Codes. Because each individual address is also tied to a specific county, when that address is validated by an address validation service provider, the corresponding county data we be returned to you as well.

By programmatically accessing the SmartyStreets ZIP Code API, you can submit tens of thousands of addresses in seconds. Our servers will process it in under 30 milliseconds on average and return to you a JSON response with up to 45 datapoints about the address, including the address' county name and county FIPS Code.

Step 1. Visit our ZIP Code API demo, select "zipcode" as your input field and enter your ZIP Code.

County ZIP Code API step 1 - select ZIP Code as your input field to lookup a lot of county names of different ZIP Codes to create sample cUrl request

Step 2. Click "View API Response".

Step 3. In the "API Response" section, you will see the county listed as "county_name". County ZIP Code API step 3 - In the 'API Response' county is listed as 'county_name'

The process is facilitated by sending a simple HTTP request to the SmartyStreets ZIP Code API. Complete instructions on how to call the SmartyStreets ZIP Code API, including URL composition, Request Methods, Input Fields and Headers are found in our ZIP Code API documentation.


Programmatically Finding County Data Using a Mailing Address API

To find the county information for a large batch of specific addresses, you will want to use our US Street Address API. Since ZIP Codes and cities frequently cross county lines, entering an address to perform a county lookup is the most reliable way to get a single county returned.

Step 1. Visit our address validation API demo page and enter the address for which you would like county info.

address API county codes step 1 - Visit address validation API demo page

Step 2. Click "View API Response".

Step 3. You will then see the sample cURL request and API response. The "county_name" will appear under the "metadata" section.

address API county codes step 3 - See the sample cURL request and API response. 'county_name' appears under 'metadata' along with FIPS Code Step 4. Implement in the language of your dreams with our choice SDK's.

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