How can one trace a grand aunt named Roseanne Whitley who emigrated to US either 1900 - 1920?

To trace anyone who entered the US in the period of 1900-1920, the place to begin looking is the index to the List of Passengers arriving at various ports of Entry, i.e. The Passenger Lists. The Indexes and surviving lists for the Port of New York (called by some Ellis Island) are available on the Internet, but indexes for other ports of entry exist and can be viewed through with the help of the Family history Libraries of the Church of Jesus Christ of the Latter-day Saints (the Mormons), on commercial web sites, or by visiting appropriate branches of the US National archives and Records Administration If she can be found on the passenger lists, you will often also learn who she was traveling with, and the name and address of someone she was going to join in the US.

That then helps you focus on a state or smaller location for searching information about marriages, children, etc.

I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.