You have two ways of getting the US citizenship: awarding (by birth) and naturalization

Awarding

Generally, people are born U.S. citizens if they are born in the United States or if they are born to U.S. citizens:

By being born in the United States: If you were born in the United States (including, in most cases, Puerto Rico, Guam, and the U.S. Virgin Islands), you are an American citizen at birth (unless you were born to a foreign diplomat). Your birth certificate is proof of your citizenship.

Through birth abroad to TWO United States citizens: In most cases, you are a U.S. citizen if ALL of the following are true:
- Both your parents were U.S. citizens when you were born; and
- At least one of your parents lived in the United States at some point in their life.
Your record of birth abroad, if registered with a U.S. consulate or embassy, is proof of your citizenship.

Through birth abroad to ONE United States citizen: In most cases, you are a U.S. citizen if ALL of the following are true:
- One of your parents was a U.S. citizen when you were born;
- Your citizen parent lived at least 5 years in the United States before you were born; and
- At least 2 of these 5 years in the United States were after your citizen parent's 14th birthday. Your record of birth abroad, if registered with a U.S. consulate or embassy, is proof of your citizenship.

Naturalization

If you are not a U.S. citizen by birth or did not acquire U.S. citizenship automatically after birth, you may still be eligible to become a citizen through the normal naturalization process. Naturalization is the process by which U.S. citizenship is conferred upon a foreign citizen or national after he or she fulfills the requirements established by Congress in the Immigration and Nationality Act (INA). The general requirements for administrative naturalization include:

a period of continuous residence and physical presence in the United States;

residence in a particular USCIS District prior to filing;

an ability to read, write, and speak English;

a knowledge and understanding of U.S. history and government;

good moral character;

attachment to the principles of the U.S. Constitution; and,

favorable disposition toward the United States.

Under the Technical Corrections Act of 1994, a child under eighteen years of age who has a U.S. citizen grandparent who meets the physical presence requirements may qualify for expeditious naturalization under the Immigration and Nationality Act.

Although not entitled to U.S. citizenship at birth, the child can, through this procedure, become a U.S. citizen by naturalization without first having to take up residence in the United States. It is, however, necessary for the child to travel to the United States for the naturalization, and all applications and documentation must be submitted and approved beforehand.

This procedure must be done through the United States Citizenship and Immigration Services. The process can take from six months to a year or more.

Biological and adopted children of U.S. Citizens who are born overseas can automatically acquire citizenship (Child Citizenship Act of 2000) provided the following requirements are met:

One parent is a U.S. Citizen by birth or through naturalization;

The child is under the age of 18;

The child is residing in the United States as a lawful permanent resident alien (that is to say has entered the U.S. on an immigrant visa and has an alien resident card) and is in the legal and physical custody of the U.S. citizen parent; and

If the child is adopted, the adoption must be final. If the adoption is to be finalized in the United States, the child becomes eligible for citizenship once the adoption process is completed.

[source: http://travel.state.gov]
 [27-05-2005]