We've recently found a couple of Naturalization cards on Ancestry.com. One was for a John William Tietjen in Kings County, NY. The witness was Claus Tietjen.
Would Claus have to be a citizen already in order to be a witness?
Was the witness usually a relative or close friend?
We live within a couple of hours from DC, would we gain more information on the people on these cards by visiting NARA?