How is the gettysburg address similar to the declaration of independence?

The Gettysburg is similar to the Declaration of Independence because they both reference American ideals.

For example, Lincoln's Gettysburg Address discusses how the men who died in the Civil War did so in fighting to see whether or not this nation founded on the idea of all men being equal will survive.

This concept of "all men being equal" was actually used in the Declaration of Independence to establish America as a country where this motto would be followed.