Applications are the meat-and-potatoes of immigration research. There are many kinds of applications where one can gather such facts as places and dates of birth and marriage for the applicant as well as for their family network .
In my One Name Study, I have been working on connecting my One Name Study constituents in the United States to their places of origin in Eastern Europe. One type is the passport application that are in databases on Ancestry and Family Search. For the United States alone, FamilySearch has amassed, at least, 6 collections ( U.S. Passport Collection at Family Search ). At Ancestry, there are numerous sub-sections but the main one is the U.S. Passport Applications, 1795-1925.
Here is one crown jewel of a find for my One Name Study(2) interest :
Here is one page of Joseph Stermensky’s actual passport application which, among other details such as a physical description, states where he lived and where he was headed:
(1) - U.S. Passport Applications, 1795-1925, for Joseph Stermensky.28 June 1920. Emergency Passport Applications, Argentina thru Venezuela, 1906-1925.1919-1920.Volume 001: Czechoslovakia. Ancestry.
(2) - http://stermenszky.one-name.net/