http://chnm.gmu.edu/courses/magic/news/irish.html
Many turn of the century Americans doubted that Irish people were really of the same race.
Though it seems perfectly clear to us that Irish people are white, it seemed less clear to our ancestors. Irish immigrants and free African Americans took many of the same jobs, and experienced similar degrees of predjudice. In America in the 1840s, an immigrant worker might be seen not as "white" but Irish. The prevalence of Irish surnames among African Americans (Shaquille O'Neal, for example) reflects to some extent the common situation African and irish Americans found themselves in. This image, from Harper's Weekly in 1871, reflects some of that ambiguity as well.
The figure, which depicts Irish American rioters conforms to both Irish and black stereotypes--oversize feet, gangly, rubbery limbs, and a propensity to violence. A recent history of the Irish in America by Noel Ignatiev explains How the Irish Became White. His answer is that Irish Americans embraced racism. They adopted racial predjudice, in other words, so they would have someone to step on in their rise to economic and social assimilation.
But even as "whites," the Irish remained suspect. The second image, drawn by the the famous political cartoonist Thomas Nast for Harper's Weekly in 1876, manages to link both Irish and African Americans in "ignorance."
One is white and one negro, but they are equals--equally grotesque in appearance, equally dangerous to the republic. Most immigrant groups have faced some form of bigotry or other. Most have also found a great deal of opportunity and embraced the "American Dream."