U.S. Citizenship and Immigration Services (USCIS) provides its services in three ways: uscis.gov, a phone service, and field offices and service centers. The field offices are where all non-asylum seekers are interviewed.
The USCIS has divided field offices by regions and districts. For example, the Los Angeles district has the Los Angeles field office, the San Bernardino field office, etc. Besides processing the applications of non-asylum seekers, field offices also arrange naturalization ceremonies and provide other services/ information.