The 1930 U.S. Census is important for researchers because it was the last census to include information on immigration and naturalization, key elements in researching immigrant ancestors.

The official starting date of the 1930 census was April 1, and it took about a month to complete. Children born between the official start date of the census and the actual day of enumeration were not included. Individuals living on the official start date of the census but deceased by the actual day of enumeration were included.

Native Americans (then referred to as “Indians”) were included in the enumeration of the general population, though they were asked different questions, as were individuals in Alaska. For example, Native Americans were not asked about their mother’s country of origin, but rather, which tribe she belonged to.

Servicemen were not recorded with their families in the 1930 census; they were treated as residents of their duty posts. When searching for someone in the military, don’t assume he or she will be listed in their hometown.

In my last column, I reviewed several questions asked in the 1930 census, dealing with home information, personal description, and place of birth for individuals who were enumerated. The next set of questions was headed “Mother tongue (or native language) of foreign born,” subtitled “Language spoken in home before coming to the United States.”

As previously noted, an immigrant’s place of birth was to be listed as the present (1930) name of the country where he or she was born. The answer to the language question is important, because it addresses the ethnicity of the individual.

For example, a person who was ethnically Polish may have been born in Prussia (which conquered parts of Poland), with a birthplace listed as Austria (the 1930 name), but the “mother tongue” column would show “Polish” as the language spoken. This can help in locating the actual town of birth.

The next set of questions come in three columns under the heading “Citizenship, etc.” First, “Year of immigration to the United States,” then “Naturalization,” and then “Whether able to speak English.” You must appreciate that the date of immigration is a secondary record; that is, it was the date given by an individual from memory, with no documentary evidence. However, it was generally given correctly, within one or two years.

The immigration year can be used to narrow down searches for passenger manifests. The date can also be compared to the answer given for “Year of first marriage” to estimate whether the person was married before or after coming to the U.S. If the person was married before immigration, a marriage record should exist in the town of origin; if after, you should search church and civil records from the U.S. locality where the immigrant lived.

In the “Naturalization” column, you’ll find one of the following abbreviations: “Na” (naturalized); “Al” (alien); or “Pa” (papers applied for). If the note is “Na” or “Pa,” you can assume that the individual applied for or was granted U.S. citizenship after the date of immigration and before April 1, 1930.