My grandfather was a member of the KKK in Tower City PA long before I was born. My mother use to watch the cross burning on the mountain during 1925 for her upstairs bedroom window. She was 5 years old. It was the Irish that were their target in the mines at that time.
I think it was more religious than ethnic .
My grandfather married an Irish Catholic woman, but his grandfather commanded a police precinct in New York City during the Civil War, including the draft riots after Gettysburg. My grandfather was raised vehemently anticatholic and his kids (including my father) were raised Dutch Reformed. He forbidden to enter a Catholic church.
My gggrandfather was a member of the Molly Maguires and so was my ggrandfather. My ggrandfather who was 10 when he arrived in PA served in the Union Army in San Francisco during the Civil War and eventually died of Black Lung from working in the mines around Houtzville and Centerville, PA. He had 13 children — 11 lived to maturity. One of his sons died in a Christmas Eve mine collapse in the Centerville area.