If you're conducting genealogical research, you want to know when your ancestors arrived in the United States and where they lived. To do so, you can access naturalization records through various sources. Your forebears became "naturalized," or underwent the process of becoming U.S. citizens. To get started, you'll need the individual's name and country of origin. Additional information, such as the year he immigrated, birth date, marital status and spouse's name, makes the search somewhat easier.
The Internet makes searching for naturalization and other genealogical records relatively simple if you have your ancestor's basic information. United States Citizenship and Immigration Services offers naturalization records of the deceased for a fee, while the National Archives has a microfilm catalog you can search. If you find microfilm that might be useful, you can buy it or visit the National Archives to conduct research or hire someone to do it for you. Private organizations offer Internet-based research tools for a fee.
Before 1906, any court at any level could grant citizenship. Information from state and local courts generally isn't available in the National Archives. If your ancestor became a naturalized citizen prior to 1906, contact the appropriate state's archives and ask for a search of records on the local, county and state level. The National Archives has regional facilities that can search pre-1906 federal records. If your family member arrived after 1906, those regional facilities are likely to have records of the naturalization.