passport v. DHS letter

[maddief]

I am confused about a particular issue concerning my grandfather (who has been dead for some time). He had an American passport and social security number but a letter from the Department of Homeland Security confirmed that there are no records of his naturalization. He immigrated to the States in the early 1900s. At that time, was it possible for him to become an American citizen without naturalization? I'd appreciate if someone could shed some light on the matter.

[Cathynap]

Did he join the armed services? Many Italians during the WWI era joined the army to fast track them through immigration (you cannot do this anymore). They would be able to obtain their citizenship just prior to checking in at their assigned post.

[maddief]

No, he wasn't in the armed services (at least, not to my knowledge). Is there any other way he would have had a passport, etc. and not have naturalized? I'm just confused.