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

To create unity throughout the poem

Allusion and illusion. an allusion is an indirect reference, whereas an illusion is something that is unreal or incorrect. each of the nouns has a related verb form: allude “to refer indirectly to,” and illude (not a very common word), which may mean “to delude or deceive” or “to subject to an illusion.”