U.S. citizens are those individuals who were born in the U.S. as well as those born elsewhere to a parent who is a U.S. citizen. In addition, there are those who choose to become naturalized U.S. citizens by filing an Application for Naturalization, Form N-400, with the U.S. Citizenship and Immigration Services, which is part of the U.S. Department of Homeland Security, and meeting the following requirements of U.S. law:
- Be at least 18 years of age;
- Be a lawful permanent resident (green card holder);
- Have resided in the United States as a lawful permanent resident for at least five years;
- Have been physically present in the United States for at least 30 months;
- Be a person of good moral character;
- Be able to speak, read, write and understand the English language;
- Have knowledge of U.S. government and history; and
- Be willing and able to take the Oath of Allegiance. 
The average annual number of individuals who became U.S. citizens increased from less than 120,000 during the 1950s and 1960s to 210,000 during the 1980s, and 500,000 during the 1990s. In the 21st century the annual average has increased to nearly 690,000 as shown by the following statistics:
|Fiscal Year||Total New Naturalized U.S. Citizens||Fiscal Year||Total New Naturalized U.S. Citizens|
Until the 1970s, the majority of persons naturalizing were born in European countries. In the 1970s the regional origin of new citizens shifted from Europe to Asia due to increased legal immigration from Asian countries, the arrival of Indochinese refugees, and the historically higher naturalization rate of Asian immigrants. This summary from the U.S. Government, however, fails to aggregate the people from South America, Central America, Mexico and the Caribbean into a Latin American group. For the latest available fiscal year (2013), the new citizens came from the following regions of the world:
|Region of origin||Number||Percentage|
In FY 2013, the top countries of origin for naturalization were in the following order: Mexico, India, the Philippines, Dominican Republic, China and Cuba.
In FY 2013, 75 percent of all individuals naturalizing resided in 10 states (in descending order): California, New York, Florida, Texas, New Jersey, Illinois, Virginia, Massachusetts, Georgia and Pennsylvania. That same fiscal year the leading metropolitan areas of residence were New York-Northern New Jersey-Long Island, NY-NJ-PA (17.5 percent); Los Angeles-Long Beach-Santa Ana, CA (9 percent); and Miami-Fort Lauderdale-Pompano Beach, FL (8.6 percent).
These new citizens provide an infusion of new perspectives on culture and on the U.S. itself. We are blessed to have them join us. Many other industrialized countries like Japan do not have this openness to newcomers and, therefore, struggle with aging and declining populations and resulting diminished influence in the world.
Although the public information for becoming a naturalized citizen on the website of the U.S. Citizenship and Immigration Services, which is the basis for this post, is very useful, anyone thinking of doing so should consider consulting with an U.S. attorney with experience in this area of the law.
 There also are other provisions for naturalization for members of the U.S. military and for children under the age of 18.
 The unusually large number of new naturalized citizens in FY 2008 was due primarily to applications received in advance of a fee increase in calendar 2008 and to a special effort to encourage eligible individuals to submit applications for citizenship.