Passenger lists
Ship passenger lists are the first US-side record of an immigrant. Pre-1820 lists are spotty; post-1820 lists are a federal requirement and survive for most arriving ports. Ellis Island (1892–1954) is the best-known but far from the only: Castle Garden preceded it in New York, and Boston, Philadelphia, Baltimore, and New Orleans also handled large volumes. Post-1906 manifests carry place of birth, last residence, name of nearest relative in the country of origin, destination in the US, and name and address of the person joining — a near-complete family sketch on one page.
The two-step naturalization process
For adult male immigrants, naturalization was a two-step process. The declaration of intention ('first papers') could be filed after two years of residence and declared the intent to renounce foreign allegiance. The petition for naturalization ('second papers' or 'final papers') was filed at least three years later and, when granted, produced a certificate of naturalization. Pre-1906 naturalization could happen in any court of record — county, state, or federal — and the records are scattered. Post-1906 records are federal and indexed centrally.
Women derived citizenship from husbands before 1922 and could not naturalize independently; after 1922, married-woman naturalization is documented separately. Children under 18 were naturalized with their father.
What each document shows
The petition for naturalization post-1906 is the richest single source: full name, current address, occupation, birth date and place, date and port of arrival, name of vessel, spouse's name and birthplace, each child's name and birth date and place, and witnesses. The certificate itself is thinner but is often the only document the family kept.