Final answer:
The key message in Lincoln's Gettysburg Address was that the Union must continue to fight for equality and preserve the democratic government. Lincoln emphasized the importance of the Union soldiers' sacrifice and the guarantee of freedom and equality for all. He concluded with the significance of a government of the people, by the people, for the people.
Step-by-step explanation:
The key message in Lincoln's Gettysburg Address was that the Union must continue to fight to fulfill the promises of equality as stated in the Declaration of Independence and preserve the democratic government of the Union.
Lincoln spoke about the significance of the Union soldiers who had died at Gettysburg and declared that their sacrifice was not only to preserve the Union, but also to guarantee freedom and equality for all.
In his famous closing statement, Lincoln emphasized the importance of a government of the people, by the people, for the people, which should not perish from the Earth.