According to Lincoln, why was the sacrifices made by the soldiers at Gettysburg worth the price they paid?

I believe the correct answer is that they died to protect American democracy.

Many sacrifices were made during the Gettysburg battle in 1863, where Union and Confederate soldiers fought within the American Civil War. Many of them died fighting for what they believed in, and when finally the Union won, Lincoln said that their sacrifices were necessary in order to preserve the American union and fight for its democracy.