Where Do You Mail an N-400 Application for Naturalization To?
According U.S. Citizenship and Immigration Services in 2015, express mail deliveries of the N-400 naturalization form should be sent to USCIS, Attn: N-400, 1820 E. Skyharbor Circle S, Suite 100, Phoenix, AZ 85034. For standard mailing options, consult the U.S. Citizenship and Immigration Services website for state-specific addresses.