If you are not a US citizen by birth or did not acquire citizenship automatically after birth, you may still be eligible to become a citizen through the normal naturalization process. If you are are 18 years and older, you use the "Application for Naturalization" (Form N400) to become naturalized. If you acquired citizenship from parent(s) while under 18 years of age use the "Application for a Certificate of Citizenship" (Form N600) to document your naturalization. If you are an adopted child who acquired citizenship from your parent(s) use the "Application for a Certificate of Citizenship on Behalf of an Adopted Child" (Form N643) to document your naturalization.
