History of South America

What does Lincoln mean by saying the brave men living and dead who struggled here have consecrated it?

By saying that the brave men, living and dead, who struggled at Gettysburg have consecrated it, Lincoln means that their sacrifices have made the ground sacred and worthy of reverence. He is suggesting that the battlefield is now a hallowed place because of the blood that has been shed on it. This idea of consecration is a religious one, and it suggests that the sacrifices of the soldiers have given the battlefield a special significance.