The New York Times has provided me with much to go on for my Diaspora ponderings with this interactive map they have published, highlighting how foreign-born groups have settled in the U.S. from 1880 until 2000.  You can see all the different groups as a whole, or select a country of origin, view impacts of largest foreign-born groups in each county across the whole country, and adjust the time slide from decade to decade between 1880 until 2000 to observe how patterns have continuously changed (and will continue to do so).  So I have lots of reference points to explore.