Lincoln’s main objective in his Gettysburg Address was to unite the nation again and regain the purpose of being a strong country. Because of that, he began his eulogy with the phrase “four score and seven years ago” which referenced to the signing of the Declaration of Independence, the major American symbol of Union and strong country.
The Declaration of Independence was signed 87 years before 1863. Lincoln began his eulogy with a reference to this event as a reminder that the Civil War soldiers were fighting and dying for freedom.
