Step-by-step explanation:
Longfellow is evoking a specific historical memory in this poem: Paul Revere and the Revolutionary War. He does this because the lessons of history can be applied to the contemporary context and be useful in understanding the present, as well as giving counsel and caution for the future. However, Longfellow takes liberties with this historical memory which leads to the question of whether or not complete veracity is necessary in order to achieve these purposes. Revere's story isn't exactly accurate but he is rendered a hero for the ages, and his deed a potent exemplar of courage and right.