Uncover the clues in historical records. This issue: Declaration of Intention
The naturalization process for a foreign-born person to become a US citizen was established in the Constitution. The process involved three steps: First, the individual had to swear and sign a declaration of intention denouncing the citizenship of another nation and allegiance to its ruler, and announcing intention to become a citizen of the United States.
After a prescribed waiting period, the person submitted a petition for naturalization. That waiting period has varied over the past two centuries, but the typical duration was five years. When submitting his petition, the person seeking citizenship swore an affidavit stating that the residency period and any other requirements had been satisfied. A witness who knew the applicant also swore an affidavit.