Briefly explain one historical event or development in the period 1863-1877 that was not explicity mentioned in the excerpt that can support Foner's interpretations

What reasons does the speaker provide to support his viewpoint or claim in what to the slave is the fourth of july i read to speech and but i just don't fully understand the question i just want to make sure i get it right so to explain that the question is asking me to do. and you!