What caused the number of African-Americans who participated in politics through voting and running for political office is arise again around 1966?

Explanation: I'm glad i saw this question because were learning about the 13th, 14th, and 15th amendments, black codes and the reconstruction in class. Anyways when the African Americans gained the freedom to vote and to be free from slavery, white people were not happy about it so they made "black codes". The black codes were meant to help black people get back on there feet after slavery and after the war, but it just mad things worse. It made things worse because African Americans were making 10 cents an hour then had to play $10-100 in taxes at the end of the year. African Americans still worked on land for money and were still treated like slaves and had been beaten on the streets by white people. In conclusion giving African American the right to vote barely did anything but in the end it all worked out.  

b - those executed came from every social and economic class