The various cases of lawful immigration to the U.S. are processed by the U.S. Citizenship and Immigration Services. The federal agency comes under the department of homeland security and services immigrants through its website, phone service, and physical offices.
The services that the USCIS provides at a field office include applicant interviews, naturalization events, and some information and other services. The network of field offices present inside the U.S. is arranged according to regions and districts. There are 4 regions and 26 districts spread across the country. A single district can have multiple field offices.