What could have happened if anything to prevent the rise of ku klux klan violence

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The first Ku Klux Klan declined in the 1870s, partly due to the passage of federal legislation aimed at prosecuting the crimes of Klansmen, though some local cells continued to operate. The institutionalization of Jim Crow segregation in the South, moreover, meant that the KKK’s desire to maintain the antebellum racial hierarchy had been fulfilled.

Use the formula: (n-2)×180, where n is the number of sides(18-2)×180= 28800, now this is the full exterior angle of 18-gon so you divide it by 18.28800÷18=160