Naturalization is the process of granting citizenship privileges and responsibilities to foreign-born residents. Naturalization papers are an important source of information about an immigrant's nation of origin, his foreign and “Americanized” names, residence, and date of arrival. Naturalization records before 1906 are not likely to give town of origin or names of parents. Information in post-1906 records is more detailed and may include birth dates, birth places, and other immigration information about the immigrant and members of his family.
Immigrants to the United States have never been required to apply for citizenship. Of those who applied, many did not complete the requirements for citizenship. Evidence that an immigrant completed citizenship requirements can be found in censuses, court minutes, homestead records, passports, voting registers, and military papers. Even if an immigrant ancestor did not complete the process and become a citizen, he may have begun the process and filed a declaration of intention. The declaration of intention can be obtained to see what information is listed on it.