Linda Thom  forwards a graphic from the Census Bureau: America’s Foreign Born in the Last 50 Years.  The whole thing is too large to reproduce in a blog post, so I'll just put in these two pieces showing migration patterns before and after the Immigration Act Of 1965 .
All of the Asian immigration pictured was actually illegal in the 1950s. Also, it's too small to show on the chart, but the fact that there is such a thing as modern immigration from Africa is unprecedented.
Well, not totally unprecedented, but it was abolished by the The Act Of 1820.