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.