Naturalization
Individuals who have been permanent residents for 5 years or longer may apply for U.S. citizenship. The application may be filed as early as 90 days prior to the 5-anniversary of the date of when the person became a permanent resident. For someone who obtained permanent residency through a marriage-based case, they may apply upon the 3-year anniversary of becoming a permanent resident (with the same option to file up to 90 days before the 3 years have passed).
Note: an individual who obtained permanent residency through employment or other means can still benefit from earlier eligibility if he/she is married to a US citizen, as long as he/she has been married to and living with a US citizen for 3 years at the time of filing (the US citizen spouse must also have been a US citizen during the requisite 3 year period).
Other general requirements include the following:
• Be at least 18 years old at the time of filing
• Show that you have lived for at least 3 months in the state or USCIS district where you apply.
• Demonstrate continuous residence in the United States for at least 5 years (or 3 years if married to a US citizen immediately preceding the date of filing. Note that a trip abroad that lasts for 6 months or longer can break the continuous residence requirement.
• Show that you have been physically present in the United States for at least 30 months out of the 5 years immediately preceding the date of filing (pro-rated for spouses of US citizens).
• Be able to read, write, and speak basic English.
• Have a basic understanding of U.S. history and government (civics).
• Be a person of good moral character.
• Demonstrate an attachment to the principles and ideals of the U.S. Constitution.
The USCIS has additional information about eligibility for naturalization at www.uscis.gov
The naturalization process typically involves four steps: (1) filing Form N-400, (2) biometrics; (3) an interview at a USCIS Field Office that includes a civics and English test, and (4) an Oath Ceremony.
Note that the United States permits dual citizenship, but not all countries do. See: https://travel.state.gov/content/travel/en/legal-considerations/us-citizenship-laws-policies/citizenship-and-dual-nationality/dual-nationality.html