Answer:
"The Gettysburg Address" is a speech given by Abraham Lincoln in 1863. which some consider to be the greatest speech ever given by any US President.
Although the largest portion of this short speech is about honoring and remembering soldiers who gave their life on the battlefield, it is important to focus on the first few sentences of the speech.
Lincoln starts by reminding everyone on the Declaration of Independence 87 years ago (four score and seven years ago). That was the document that created and shaped American nation. The most prominent pillar on which the document resides is that "all men are created equal".
Now, Lincoln argues that that belief is put to a test. And that test is Civil War. It is a test that needs to show whether a country so dedicated to freedom and equality can endure and persist.
Basically, he poses a question "How long will a country that rests on the principles of freedom and equality regard slavery as normal thing?". According to him, the answer lies in the outcome of the war.