Census records often provide valuable hints to an individual’s immigration and naturalization dates or status. This blog post will outline those clues.


Country of Birth


Each person’s state or country of birth is reported in the 1850 through 1950 censuses.  A foreign birthplace obviously indicates the person immigrated to the United States sometime between birth and the date of the census.  It is extremely important that the researcher locate the person of interest in all censuses during which the person lived in the United States for several reasons:


  • The person’s age (implied year of birth) may vary significantly from census to census and should be further verified by other records such as death records, gravestones, newspaper obituaries, and so forth.
  • The “country of birth” may be reported differently in different census years, such as “Germany” in one census and “Prussia” in another, or “France” in one census and the province of “Alsace-Lorraine” in a different one.
  • The “country of birth” may be reported under the national boundaries that existed during that census year or, possibly, as they existed at the time the person was born or lived there, depending on the instructions given to the enumerator and/or the responding person’s knowledge.  For example, see the instructions on country of birth given to 1950 census enumerators in 1950 Census:  Form P1, Population and Housing Schedule Questions for All Persons.
  • The “country of birth” may be inaccurate if reported by another family member who was not well informed.
  • “Born at sea” is sometimes indicated.  If true, it’s a great clue to a specific and narrow time-frame of arrival in the United States.  Like other census information, however, it may not be accurate. One researcher found an ancestor in the 1880 census who was said to be “born at sea” of Scottish-born parents. However, all other census records for this man indicated he was born in New York State.  The researcher also determined that the man had an older brother for whom all records indicated birth in New York State.  The researcher eventually concluded the “born at sea” statement may have been part of a tall tale the man told to his new wife and in-laws.


Date of Immigration to the United States


Locating an immigrant’s record of arrival on a ship passenger list (1820-1950s) or Canadian (1895-1950s) or Mexican (1903-1950s) border crossing arrival record requires knowing the (1) immigrant’s name at the time of his or her arrival, (2) approximate year of birth, and (3) approximate date of immigration.  The more accurate information the researcher has, the more likely the researcher will find the correct person.  Many people had the same first names and surnames.


Year of immigration to the United States is indicated in the 1900 census (column 16), 1910 census (column 15), 1920 census (column 13), and 1930 census (column 22). This is a great clue, but again, the answer to this question may vary from census to census, depending on whether the year was remembered accurately or not, and depending on the knowledge, or lack thereof, of the person who provided the information.


Decade or approximate year of immigration to the United States can be implied by information such as the person’s first appearance in a U.S. census or publications such as city directories.


If a couple’s older children were reported as born in a foreign country and their younger children were reported as born in the United States, census records implicitly suggest an approximate year of immigration to the U.S.  The year(s) between the last foreign-born child’s birth and the first U.S.-born child’s birth are likely to be the time span during which the couple and their older children immigrated to the United States.  However, the whole family unit may not have immigrated together.  For example, the husband may have immigrated first, with the wife and children following later.


Date of Naturalization and Naturalization Status


Naturalization is the voluntary legal process by which a foreign-born person becomes a citizen of the United States.


From 1790 through most of the 20th century, naturalization was a two-step process for most adult men. After residing in the United States for two years, an alien could file a “declaration of intention” (“first papers”) to become a citizen. After three additional years, the alien could “petition for naturalization” (“second papers”). After the petition was granted, a certificate of citizenship was issued to the new citizen. These two steps did not have to take place in the same court or even in the same state.  More information is provided on our “Naturalization Records” webpage.


From 1790 until September 22, 1922, a woman’s citizenship status was determined by the citizenship status of her father or husband.  Before September 22, 1922, a foreign-born woman became a U.S. citizen when she married a U.S. citizen or when her foreign-born husband became naturalized.  She could also lose her U.S. citizenship by marrying an alien.  For more information, see “Women and Naturalization, ca. 1802-1940” Part I and Part II.


Information on the person’s naturalization status in census records can help the researcher focus on a time span and courts near the person’s residence for potential naturalization records. Several censuses indicate or imply a date of naturalization and naturalization status:


  • The 1820 and 1830 censuses report the name of the head of household and the number of “foreigners not naturalized” in the household.  Although the specific person or persons in the household who were foreigners is not indicated, this clue should alert the researcher to (1) search for known household members in immigration records, (2) be alert to clues in other records that point to the suspected immigrant's possible foreign origins, and (3) search for possible later naturalization records for the suspected immigrant. Unfortunately, however, there are relatively few ship passenger lists (immigration records) before January 1, 1820, when the Federal Government began requiring such lists to be presented to collectors of customs.
  • The 1870 census (column 19) indicates with a check mark “Male Citizens of the U.S. of 21 years of age and upwards.” If the man was a foreign-born citizen, this means that he had become naturalized by 1870.
  • The 1900 census (column 18) indicates the person's naturalization status.  The answers are “Al” for alien, “Pa” for “first papers,” and “Na” for naturalized (“second papers”).
  • The 1910 census (column 16) indicates the person's naturalization status.  The answers are “Al” for alien, “Pa” for “first papers,” and “Na” for naturalized (“second papers”).
  • The 1920 census (column 14) indicates the person's naturalization status.  The answers are “Al” for alien, “Pa” for “first papers,” and “Na” for naturalized (“second papers”).
  • The 1930 census (column 23) indicates the person's naturalization status.  The answers are “Al” for alien, “Pa” for “first papers,” and “Na” for naturalized (“second papers”).
  • The 1940 census (column 16) indicates the person's naturalization status.  The answers are “Al” for alien, “Pa” for “first papers,” and “Na” for naturalized (“second papers”).
  • The 1950 census (to be released for public use on April 1, 2022) (column 14) indicates “Yes” (naturalized) for persons who had taken out their “second papers” or were naturalized through either parent when the person was a minor.


In addition to indicating naturalization status at the time the census was taken, these clues suggest when the person’s naturalization status changed.  For example, if an ancestor is listed as an alien (“Al”) in the 1920 census and is then listed as “Pa” or “Na” in subsequent censuses, the researcher will know to look for naturalization records for that person after 1920.


Special note:  Persons born abroad or at sea of American parents are listed in the citizenship column with the codes “Am Cit” in the 1940 census, and “AP” in the 1950 census.


Solid genealogical research requires using information found in one record as hints to help locate other records about the same person or family unit.  Census records provide valuable clues that assist the researcher in locating immigration and naturalization records.