Assuming that you qualify for US citizenship at birth, you can apply for proof of your citizenship by applying for a US Passport with the Department of State on form DS-11 or you can apply for a Certificate of Citizenship with the Department of Homeland Security on form N-600. You will also need to submit your original Birth Certificate, your father's original Birth Certificate, your father's original Marriage Certificate, and proof of your father's residence in the US for a certain number of years prior to your birth. Proof of residence can include, but is not limited to: junior high/high school/college records, medical records, tax records, bank records, employment records, etc. A US Passport will cost about $100, while a Certificate of Citizenship will cost about $600.
Answered on Aug 09th, 2013 at 7:33 PM