Citizenship is one of the most coveted gifts that the U.S. government can bestow, and the most important immigration benefit that USCIS can grant. Most people become U.S. citizens in one of two ways:
By birth, either within the territory of the United States or to U.S. citizen parents, or By Naturalization.
In addition, in 2000, Congress passed the Child Citizenship Act (CCA), which allows any child under the age of 18 who is adopted by a U.S. citizen and immigrates to the United States to acquire immediate citizenship.
All persons born or naturalized in the United States, and subject to the jurisdiction thereof, are citizens of the United States and of the state wherein they reside. No state shall make or enforce any law which shall abridge the privileges or immunities of citizens of the United States; nor shall any state deprive any person of life, liberty, or property, without due process of law; nor deny to any person within its jurisdiction the equal protection of the laws. - XIV Amendment to the U.S.