Prepared by Elisabeth Lindsay.
The word "alien" means "foreign," and can refer to many things, including a being or thing that is foreign to its present environment such as a person from another country (or even another world); a concept that is foreign, or a foreign substance. In genealogy, the term is typically used to refer to a non-citizen resident: a person other than a native-born or naturalized citizen.
The term is often seen in official records relative to immigration, naturalization, and citizenship or nationality. For example, the 1910 to 1930 U. S. Federal Census used he term "alien" to refer to non-citizens; researchers may find the term abbreviated as "AL," which indicates the immigrant had not begun the naturalization process and was still an "alien" at the time the census was taken. The U.S. and other countries, at various time have required alien registration other than for the purposes of naturalization, which could occur upon entering the country, granting the right to work or own property, and alien registrations during wartime.