According to the U.S. 2000 Census, roughly 9 million people claim Polish descent -- with the largest Polish populations in New York (986,141), Illinois (932,996), Michigan (854,844), Pennsylvania (824,146), and New Jersey (576,473) (http://factfinder.census.gov).
The Polish American immigrant experience is a compelling one -- from around 1608, when Polish immigrants first appear in the Jamestown, Virgina archives to later waves of immigrations leading up until the Cold War and beyond.
While some claim Poles arrived on Viking ships exploring the New World before 1600, to date there hasn't been any evidence to support such claims. Records indicate the first appearance of Poles in America as early as 1608, when they were recruited to the colonies to establish artisan industries. See Wikipedia, Polish American, http://en.wikipedia.org/wiki/Polish_American (describing the history of Polish Americans) (as of May 28, 2011).