Naturalization" is the legal term for the process of acquiring United States citizenship after birth. In order to naturalize, a foreign citizen or national may apply for U.S. citizenship after he or she complies with certian requirements. Applicants for citizenship must establish that they qualify to become U.S. citizens based on residence and physical presence, good moral character, knowledge of English language, US history and government, and loyalty to the United States.

In order to qualify for citizenship, an applicant must be a permanent resident, and have lived in the U.S. for a certain period of time. If the applicant became a permanent resident through marriage to a U.S. citizen, the applicant may apply for citizenship after residing in the U.S. for three years since obtaining permanent residency or conditional permanent residency. Otherwise, the applicant must have resided continuously in the U.S. for at least five years, and been physically present in the U.S. for at least 30 months of those five years.

    In order to qualify, the applicant may not have any single absence from the U.S. of more than one year (absences of more than six months but less than one year are considered to disrupt the applicant's continuity of residence unless the applicant can establish that he or she did not abandon his or her residence during such period). The INS treats time spent in the service of the U.S. Armed Forces as time physically present in the U.S., even if the applicant was out of the country. Finally, the applicant must have resided within a state for at least three months.

An applicant for citizenship must be a person of "good moral character" during the required permanent residency period (although the INS may also look at events that occurred prior to residency to determine character). Persons who have been convicted of aggravated felonies (committed on or after November 29, 1990) or who have ever been convicted of murder are permanently barred from applying for citizenship on this basis. Any applicant with a criminal record should consult an immigration attorney prior to applying for citizenship, because many crimes that make a permanent resident ineligible for citizenship also make him or her deportable as well. Not all crimes result in a permanent bar to citizenship, and not all crimes will prevent a finding of "good moral character."

At the time of the naturalization interview a test is given to determine the applicant's knowledge of basic English, U.S. History, and Government. The test requires that the applicant write a sentence in English dictated by an INS officer, and a number of multiple choice questions about American history and U.S. government. Applicants for naturalization must also be able to read, write, speak, and understand basic English in order to qualify for citizenship.

There are certain exemptions for persons who are over a certain age and have been present in the United States for very long periods of time, and for persons who demonstrate that they have a physical or mental impairment which affects their ability to learn English.

Once an applicant is approved for naturalization, he or she must take the oath of allegiance in a ceremony actually conferring citizenship. The applicant swears to support the Constitution and obey the laws of the U.S., renounce any foreign allegiance and/or foreign title, and bear arms for the Armed Forces of the U.S. or perform services for the government of the U.S. when required.

Individuals that do not fulfill the requirements above may be ineligible to become a naturalized citizen. Additionally, there are certain classes of people that are automatically barred from naturalizing to the United States. Anarchists, individuals who advocate or teach opposition to organized government, people affiliated with the communist or other totalitarian party, persons who advocate the overthrow of the US government, saboteurs, or persons who publish subversive material regarding violent overthrow of government are all such classes of people. A person who has deserted the US armed forces or has pending deportation proceedings against them is automatically barred from naturalizing to the United States.

One of the most obvious benefits and responsibilities bestowed upon a U.S. citizen is the right and duty to vote and participate in the political process that shapes the nation. Additionally, a naturalized U.S. citizen is entitled to all the benefits of traveling abroad on a U.S. passport, including relative freedom of movement throughout the world without having to comply with burdensome visa requirements. Serving on juries is another responsibility of citizenship.

Some of the greatest benefits for naturalized citizen are immigration benefits. For example, only U.S. citizens are permitted to petition for their parents, siblings, or for their married children. U.S. permanent residents are not. Also, only a certain number of immigrant visas are available each year for the spouses and minor children of U.S. permanent residents.

Spouses and minor children of U.S. citizens are entitled to an immigrant visa immediately. The unmarried adult sons and daughters of U.S. citizens are generally on a shorter waiting list than those of permanent residents.

Many immigrants do not realize that permanent residents may, under certain circumstances, be stripped of their right to remain in the United States, and removed to their home countries, or refused entry to the United States upon return from abroad.
Many permanent residents convicted of crimes that are classified as "aggravated felonies" since coming to the United States became subject to removal even if they have served their sentences. The INS definition of "aggravated felony" includes many non-violent crimes, e.g., shoplifting and check kiting. The law also was made retroactive, so long-term permanent residents who have criminal histories, even from decades ago, can be deported. The same crimes that make a permanent resident "deportable" can also result in an unexpected refusal of permission to enter the country when returning from a trip abroad.