Naturalizations ("Na" on Census Reports) are the papers that individuals submitted and received when becoming a Citizen of The United States.
Actually there are two papers that consist of "Citizenship Papers" which process took at least five (5) years to complete:
(1) The Declaration of Intent : The first papers a foreign-born person would fill out declaring that he/she (women did not usually become citizens until 1900 or so) was working towards becoming a Citizen of The United States. The Declaration of Intent usually has much more information on it than does the second (2) or Naturalization Papers-very often including the birthdate/birth place, immigration information (the port of entry which is helpful to find ship's lists), and other pertinent information. After 1900, photographs of the individual may even be found on these papers!
(2) The Naturalization Papers: The final papers declaring that the person was now a Citizen of The United States.
Both of these papers are a great resource for Family History Researchers! They may be found in different locations however which make finding them difficult sometimes if the person moved during the five years: for instance, a person may have filed their Declaration of Intent in Chicago and received their final Naturalization papers in Door County. Also, not all people applied for Citizenship as soon as they arrived in the U.S. The U.S. Federal Censuses have a box to denote if a person has applied for citizenship when the census was taken:
Pa=Previously Applied For or Na=Naturalized Citizen.
For Door County, Wisconsin (and the surrounding counties in Wisconsin), the Naturalization or Citizenship Papers are found at the Wisconsin Area Research Center in Green Bay, Brown County, Wisconsin at the Cofrin Library Bldg. of the University of Wisconsin-Green Bay (UWGB). For a very small fee you can request a search of the Citizen Papers for the person you are researching. You can request via e-mail or regular mail or can visit them in person. Be sure to remember to request BOTH the (1)Declaration of Intent and the (2)Naturalization Papers.
The following is the link to the Green Bay Area Research Center described above:
For a listing of some Door County Individuals being Naturalized as Citizens on 25 Feb 1915: