Because people during the reconstruction were fighting due to slavery (the civil war) or the rights of african americans. The civil right movement was like a continuation or amendment of that reconstruction era to guarantee people of all races the same rights and abolish racial segregation; this actually never came to light when slavery was abolished and the reconstruction era ended.
The United States Constitution provides that the House of Representatives "shall have the sole Power of Impeachment" ( Article I, section 2 ) and that "the Senate shall have the sole Power to try all Impeachments…[but] no person shall be convicted without the Concurrence of two-thirds of the Members present
