How do you become a US citizen?

Citizenship comes by birth or by naturalization. Anyone born in the United States is a citizen under the Fourteenth Amendment, with narrow exceptions for children of foreign diplomats, and children born abroad to citizen parents generally acquire citizenship at birth subject to residency requirements that depend on the parents' history. Everyone else naturalizes, which begins with lawful permanent residence, the green card, and requires holding it for five years, or three years for those married to and living with a US citizen, with physical presence in the country for at least half that period.

The application is Form N-400, filed with US Citizenship and Immigration Services with a fee that has a reduced rate and waiver for lower incomes. The process includes biometrics, a background check, and an interview at which an officer tests English speaking, reading, and writing, and administers a civics test drawn from a published list of questions about American history and government, with exemptions and accommodations for age, length of residence, and disability. Good moral character during the residence period is required, and certain criminal convictions bar naturalization permanently. Processing times vary considerably by office and have ranged from several months to well over a year.

The final step is the Oath of Allegiance at a ceremony, after which the person is a citizen with the right to vote, hold a US passport, sponsor relatives, and hold most federal jobs, and without the risk of deportation. Two points frequently misunderstood. The United States permits dual citizenship in practice, and naturalizing does not require renouncing another nationality under US law, though the other country's law may differ. And the citizenship test is public, with the questions and acceptable answers posted by USCIS, which is why study materials are free.