In the U.S., it’s the U.S. Citizenship and Immigration Services (USCIS) that handles all immigration cases except the asylum ones. The USCIS comes under the Department of Homeland Security (DHS) and has a presence across the country and territories.
The physical location of the federal agency where it processes immigration applications is called a field office. Each field office has its own field director. There can be multiple field offices within a State. In terms of organization, the USCIS uses a system of Districts. There are a total of 26 Districts and a district may have jurisdiction over counties in more than one States. Above the districts are the Regions – four in total (Western, Central, Southeast, and Northeast).
If you’re unsure about the location of a field office then the office locator tool of the agency is a good way to finding that location. The tool provides up-to-date information using your zip code as a reference. Of course, the information may also be available on secondary websites and search engines, but it may not show the current address of the office.