The best magazine
Birth Certificate
The most commonly sought after and approved proof of citizenship of the United States is your birth certificate as issued by the city, county, state or outlying possession in which you were born.
Birth Abroad
A U.S. Certificate of Birth Abroad or a Report of Birth Abroad of a U.S. Citizen form are acceptable proof of citizenship for those who were born abroad to United States citizens.
Other Certificates
Other certificates proving your residency or citizenship include a certificate of naturalization, a certificate of citizenship, a U.S. citizen identification card and, in some cases, a U.S. passport.
Green Card
The Immigration and Naturalization Service (INS) Form I-551, alien registration receipt card, is a widely accepted proof of your legal residency in the United States. This card is commonly referred to as a "green card."
Considerations
Each entity to which you need to provide proof of residency or citizenship may require different forms of proof. Birth certificates and INS documentation and cards are the most commonly accepted forms of proof accepted. Generally, your proof will have to be signed or stamped and issued by an agency of the United States.
Source: ...