When did immigrants first become citizens of the US?

How would I trace the citizenship status of Mother Theodore Guerin,
founder of the Sisters of Providence at St. Mary-of-the-Woods,
Indiana?  She came to the United States in 1840 and died in 1856.

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Request for Question Clarification by politicalguru-ga on 21 Oct 2003 05:30 PDT

Dear Kathy Anna, 

Naturalisation already existed in the years you're discussing. 

I've found where to locate such records from 1840 (off line resource).
However, there is no guarantee that the records will be found there. I
could be, that she was never a US citizen (also today, not every
immigrant is naturalised) or that her records are misplaced, lost,
etc.

Did you already contact the Diocese of Vincennes / Indianapolis -
Archdiocese ? They have an archive (at least some of it in Notre
Dame), where they might have copies of such information.