Before Simmons "re-founded" the Klan in 1915, there was the Lily White movement to which i alluded, and it was popular all over the nation--but most especially in the Old South and in the West. There had been race riots (and would continue to be) in northern cities, but many blacks, disillusioned by their experiences in the North, had moved west.
The Klan became equally as popular, and as widespread, but the unlike the Lily Whites, who were acceptable at a church social, the Klan was an activity for the edge of town, and in the dark of night. Much of the iconography of the modern Klan came directly from Dixon's novel, via Griffith's
The Birth of a Nation.
In the poster below, you can see the origin of the Klan robes, and note that the night rider here has a burning cross in his hand:
In this still from the motion picture, Klan members prepare to lynch a black man:
The motion picture, as well as the Klan, was quite as popular in the North and in the West, as in the Old South. The NAACP was founded after a race riot in Springfield, Illinois--Lincoln's "hometown"--which was itself sparked by a Klan style lynching of a black man. It has been alleged (and i believe, with good reason and inferential sources) that Klan members would not parade in their regalia, nor wear it when they intended to lynch someone, or burn a family out of their home--the organization continued to maintain a public face for quite a long time. In 1972, a friend and i convinced a Klansman in white robe, accompanied by a Klan security agent in a helmet liner spray-painted silver and carrying an M1 carbine, to pose next to a Newport News city police cruiser, with two officers inside--all of them smiling--which we then photographed. They apparently saw nothing wrong with being photographed in that manner, nor seemed suspicious of our motives. Of course, i was able to talk just like them, so we didn't have any of that "you ain't from around here, are ya?" problem.