When looking at deed indexes, be sure to look at both the "Grantor Index", an index to those selling the land and the "Grantee Index", an index to those buying the land.
The 1900 through 1930 censuses lists the individual's year of immigration to the United States. Don't be surprised if they are all different dates.
Source: Derivative Materials that offer alternate versions of the original: this source is abstracted, compiled, formed into a database, transcribed, translated or otherwise derived from the original.
[Sources & Evidence]
Vital Records include birth, marriage, divorce and death records.
Digital copies, sometimes called "portable files", are copies of your original documents, family group sheets, notes, pedigree charts, etc.