How do I know if I am eligible to become a US citizen through naturalization?

You are eligible to be naturalized and become a US citizen if you are a permanent resident, you have a valid alien registration card (green card), and you have lived continuously in the United States for at least five years (or three years if you are married to a US citizen sponsor). In addition, you must be of good moral character; have an understanding of US history and civics; be willing to take an oath of allegiance to the United States; and be able to read, write, and speak English and pass the Citizenship Test.