What were the scriptural arguments used for modern western racism?

A blight on the modern western church is that the bible has been used by certain people to justify racism--specifically dark-skinned people's inferiority and light-skinned people's superiority. Some unfortunately smart people found passages of scripture to support this viewpoint and created compelling arguments. **What are these arguments for racial superiority and from which scriptures do they come?** And I'm not just asking about slavery! For example, how did the American church support ideas like segregation and Caucasian superiority into the '30s and '40s and '50s, long after the days of emancipation?