Citizenship can only be gained one of two ways; through birthright or through naturalization. Birthright covers all persons born on U.S. soil, born to U.S. citizen parents or born to U.S. citizen grandparents. Naturalization refers to persons who acquire citizenship through legal residency in the United States. Once gained, however, there is no distinction between a birthright citizen and naturalized citizen; both have the same rights and are considered equal under the law.
Any person born on U.S. soil regardless of parental status (such as an illegal immigrant parent) is automatically an U.S. citizen. All persons born to either an American mother or father outside of the United States are also automatically a U.S. citizen as well. Persons born to American grandparents outside of the United States also qualify for citizenship, though citizenship must be registered (applied for).
In order to qualify for citizenship, you must be a legal resident. Those who are not residing legally in the United States (illegal immigrants or residents on expired visa) do not qualify. Visas that can lead to legal residency (a green card) include family, work, marriage, refugee or lottery visas.
All legal residents must complete a period of residency before becoming eligible for citizenship. The residency period is five consecutive years for all residents except those married to U.S. citizens (immigrants who entered on K-1 or K-3 visas). The period of residency for spouses of U.S. citizens is only three years. Residency implies being physically present in the United States and not simply owning an address. Any LPR (Legal Permanent Resident) who travels outside of the United States for a period of one or more years without obtaining a reentry permit to do so is likely to be stripped of their status. Reentry permits (I-131 Application for Travel Document) allow LPRs to remain outside of the United States for periods of one to two years without losing their status. However, in order to maintain the residency status (over a five-year period) needed for citizenship, an LPR must file N-470 Application to Preserve Residence for Naturalization Purposes simultaneously with I-131.
Moral character is another requirement for citizenship. The evaluation of moral character is based on criminal record, tax record and whether or not the LPR can financially support themselves and their dependents. Felony convictions are serious blocks in a citizenship application, and conviction, whether of a serious offense or misdemeanor, can result in the denial of citizenship as well as deportation from the country and future banishment.
English and American Civics
All citizenship applicants are required to hold basic knowledge in the English language and American civics before earning citizenship (citizens from English-speaking countries are not required to sit through the English examination). At the interview, tests are given on English reading, writing and speaking, as well as basic U.S. history and governance.
Application and Ceremony
Qualified applicants must submit form N-400 Application for Naturalization to the USCIS along with the $675 application fee and a copy of their green card. After the interview, applicants who pass must attend a citizenship ceremony, where the swearing of allegiance to the flag is performed and citizenship certificates are awarded.