The road to U.S. citizenship can be very long. In most situations, a person cannot apply for naturalization (i.e., U.S. citizenship) until he or she has been a U.S. permanent resident for five years.
If a person is married to a U.S. citizen and has been living in marital union with his or her U.S. citizen spouse for three years, that person may be eligible to apply for naturalization when he or she has been a U.S. permanent resident for only three years. Any person who obtained U.S. permanent resident status as a battered spouse or child of a U.S. citizen may also be eligible to apply for naturalization after three years in permanent resident status.
There are some exceptions, including the case of a person who has served in the U.S. military for at least one year. There is no requirement that the person first obtain U.S. permanent residence before applying for naturalization.
Other exceptions include, but are not limited to, a person whose spouse is a U.S. citizen regularly stationed abroad due to his or her employment and a permanent resident whose spouse is a member of the U.S. Armed Forces and is stationed abroad.