Racism started with the Muzzies and Arabs in 550AD, and expanded to the Europeans. Religion facilitated racism. Side by side, they were used to do the work of the Lord.
From a sick Eugenics notion, the jump was made to the insane ideology that a person with a specific skin color is superior to others with different skin tones. The concept of race started with the Romans who decided that physical differences were the result of environmental factors. Then, at some point in time, humans were divided in distinct groups when George Cuvier came up with three different races; James Cowles Prichard decided on seven; Louis Agassiz found twelve, and Charles Pickering counted to eleven. It wasn’t long before Christoph Meiners, born in Warstade, a German practitioner of scientific racism, chimed in. Soon enough, an idiot named Francis Galton, a pioneer of Eugenics, took over and transformed what became virulent racism to a new level. It became a powerful weapon to foster fear and hatred. Skin color was officially linked to the purification of American society.
Like religion, it was easy to spread to the ignorant masses.