Prior to 1906, these papers would sometimes show age, port of arrival, and date of arrival in the U.S. After 1906, they specifically ask for village of birth, name of ship, and both dates and ports for departure and arrival.
Useful clue: The 1920 census asks for the year a person was naturalized. This should help you locate two important papers that were then filed during the naturalization year:
These two steps in the process may have taken place in two different states or courthouses.
Also worth noting: When immigrant wives of naturalized citizens became widows, they were required to go through the naturalization process.
Naturalizations were also done by the U.S. District Court located in Rockford.(Click here for more information.) Check both the Circuit Court and the District Court Records.