If the southern US has not historically been more hostile to blacks than other regions of the US, then why did almost every major event of the civil rights movement of the 50s and 60s take place in southern states?

Why were most of the jurisdictions requiring preclearance to change their voting laws under the Voting Rights Act of 1965 in the south? Its because those counties and states have had a documented history of limiting the voting rights of minorities, specifically blacks.