It was common to regard the Irish as subhuman. This website has numerous illustrations from the nineteenth century depicting the Irish as simian or simply subhuman.

hi! there have been a few threads about "whiteness" in general; most posts at least touch on the Irish

Europe had normal diplomatic relations with non-white nations before turning explosively racist to justify their actions against all others. What happened to cause this shift?

How exclusive was 'whiteness' in the 19th century? How did it expand to include other nations throughout the 20th century?

How have various ethnic groups in the US been assimilated into the umbrella labels of "white" or "American"? (Also curious about whether something like this has happened in other countries, and how.)

How well did the European immigrants to the United States of America who weren't of north and north western stock fit into the dychotomy of black-white?

How did the concept of "whiteness" as a racial identity develop and change over time?

When and how did ethnic groups such as Irish and Italians become "White"?

Were Irish people white...in the USA in 1931? (cross-posted from AskReddit)

When and why did Irish, Poles, Italians, and other nominally white minorities get a race-lift to White?

Before the Irish became "white" in the US, how were people able to distinguish them as "non-white?"

How has the notion of' whiteness' changed since colonisation?

... and I recall one about Swedish immigrants in the US, but can't find it. And I believe there were a few more, so search away :)