Interactive Immigration Explorer By New York Time

I just came across this really interesting interactive tool from the New York Times that tracks geographic settlement patterns of major racial/ethnic immigrant groups throughout the United States by decade, from 1880 to 2000: the Immigration Explorer.

For every group included in the graphic, you will notice that as the decades pass, their settlement patterns become more dispersed throughout the country. In other words, in the past, immigrants would concentrate in the traditional major metropolitan areas of New York, Los Angeles, San Francisco, and Chicago.

Also, just 20 years ago, people from Eastern and Western Europe were still considered immigrants. Today, they are kind of lumped into the category of "White". So, what's exactly is the definition of "White"?