Why did the limestone have to come to the pyramid via water?

The battle of the Antietam affected the focus of the civil war by leading to the emancipation proclamation.

Explanation: The Battle of Antietam was important to the Union Army, as their goal was to keep the Confederate forces from encroaching onto Union soil. This battle is considered by many historians as a tie. However, General George B. McClellan did his job by forcing the Confederate Army to retreat back into Virginia. This retreat by the Confederate Army convinced President Abe Lincoln that the Union had "won" the battle and he could finally give the Emancipation Proclamation. If the Confederates won this battle, he would have not given this address due to their close proximity to the nation's capital.