This image represents the second half of the 19th century, mainly the Reconstruction era (1863-1877)
The first Ku Klux Klan was a right-wing extremist organization which emerged in the Southern States during the 1860s decade and which lasted until the late 1970s. They fought for the purification of the American society, they were white supremacists and conducted attacks against African American leaders and civilian population. They were characterized by wearing white gowns and conical hats, like the man in the image.