Why did Lincoln give the Gettysburg Address?

The Battle of Gettysburg, although a Union victory, cost the Army of the Potomac some 23,000 lives. It was such a large loss of lives (for both sides) that Lincoln was asked to come to say a "few words" at the dedication of a battlefield cemetery. Lincoln took the opportunity to encourage the people of the North to continue the struggle to save the Union. The brief inspirational speech became widely known and succeeded in reinforcing the morale of the North.