U.S. citizenship can be aquired through a process called "naturalization". The eligibility requirements for naturalization vary, and are outlined as follows:

• Length of time as permanent resident. Applicants must be permanent residents for five years before applying for naturalization. The exception is if the applicant has been married to a U.S. citizen for three years before applying, and the U.S. citizen spouse has been a U.S. citizen for at least three years.
  
  
• Continuous Residence. Applicants must have resided in the U.S. for five years, without absences of six months or longer. For applicants married to U.S. citizens, the length of continuous residence is three years.
  
  
• Physical Presence in the U.S. Applicants must have been physically present in the U.S. for at least half of the time that they were required to reside - either thirty months or eighteen months.
  
  
• Time in District or State. Applicants must reside in the district where they file for at least three months before filing.
  
  
• Good moral character. The CIS makes a determination of an applicant's "moral character" by considering any prior criminal acts and any evidence of lying or misrepresentation. Applicants must meet the "good moral character" requirement.
  
  
• Knowlege of the English language and American civics. Applicants must demonstrate knowledge of the English language, and must correctly answer a given number of civics questions.
  
  
• Attachment to the U.S. Constitution. Applicants must affirmatively answer questions relating to their attachment to the U.S. Constitution.

Exceptions apply to almost all of these requirements. Further information about the naturalization process can be found on the USCIS website at www.uscis.gov.