A person can become a US citizen in two ways: by birth in the US or birth abroad to US citizens, which is generally an automatic citizenship, or by naturalization, which requires an affirmative application and compliance with the statutory eligibility requirements.
If only one parent is US citizen, s/he must have resided in the US (be physically present) for at least 5 years (at least 2 after the age of 14) before child was born and must apply for citizenship before the child turns 18 years old. Derivative citizenship may also be transmitted from a citizen grandparent (citizen parent of citizen parent) in cases where the citizen parent cannot satisfy the physical presence requirement.
Applicants for naturalization must meet the following qualifications:
An applicant for naturalization must file form N-400 plus filing to his/her local USCIS district office.