The following is the information I copy/paste from the CIS website.
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Note: To mail in specific forms, please consult the mailing addresses below; each form sent directly to this Center has a different PO Box number and zip-code identifier.
For mailing General Correspondence, please use the address below. . However, for status inquiries do not send a letter of inquiry, instead call Customer Service at 1-800-375-5283.
U.S. Department of Homeland Security
US Citizenship and Immigration Services
California Service Center
P.O. Box 30111
Laguna Niguel, CA 92607-0111