When submitting an N-400 Application for Naturalization Form to apply for US citizenship, which USCIS field office is assigned to the application?

Question

When submitting N-400 Application for Naturalization Form (mirror) to apply for US citizenship from the US, which USCIS field office is assigned to the application?

The closest to the residence at the time of the application? The closest to the residence at the time of the application but within the same state (e.g., someone living in Vancouver, WA would be assigned to the Seattle, WA USCIS field office and not the Portland, OR USCIS field office)? Any USCIS field office in the same state of the residence at the time of the application? Did the USCIS release a map showing which districts are assigned to a specific USCIS field office? etc.

Answer 1

Reddit user Separate_Disaster828 pointed me to the following resource:

https://www.uscis.gov/about-us/find-a-uscis-office/field-offices: Scroll all the way down and type your zipcode where it says “field office locator”.

The information is confirmed by https://www.boundless.com/immigration-resources/uscis-processing-times/#wait-times-for-naturalization-applications

To handle the enormous volume of applications it receives, USCIS is supported by field offices across the United States, and each applicant is assigned to a field office based on their ZIP code. To find the office handling your case, enter your zipcode into the USCIS search box.

This matches what I was reading on https://www.dhs.gov/immigration-statistics/yearbook/2019/table23, e.g. "Portland-Vancouver-Hillsboro, OR-WA". If one indicate a Vancouver, WA zipcode such as 98662 in https://www.uscis.gov/about-us/find-a-uscis-office/field-offices, it'll indeed assign the Portland field office.