There are a wide variety of sources you may find among family and home documents. The list is too long to repeat here, and may be found in any number of beginner books about starting genealogical research. Just remember, any document about you that you may have had in your possession during your lifetime, represents a similar document about your immigrant ancestor that may have ended up with your family archivist. This includes family Bibles, passports, naturalization certificates, insurance papers, school records, church certificates and a host of others. For most 20th century immigrants, many such papers will mention their home town in the old country. However, the reason these records are so much better for recent immigrants than for earlier ones stems from two situations. First, the more recently documents were created, the less likely that they have been lost or destroyed. Second, the more time that has elapsed since an immigrant arrived with such records, the more descendants have been born and have migrated to various places in the new country. For any 18th century immigrant, these records may exist, but you may not have any way of locating where they are. Of course, some, such as photographs, can only exist since the mid- to late-19th century.