The geographical features of the country were favorable to the execution of his plans.
Ten miles west of Frederick the South Mountain rises above the surrounding country, dark, steep, rocky, and clothed with forests. Its most northern spur is near Gettysburg, Pennsylvania. There are two gaps in the range west of Frederick. If Lee could hold these with a portion of his force, he could surround Harper's Ferry, situated on the Potomac, where that winding and impetuous river leaps through the rocky gorge.
If successful in capturing it, he could still hold the mountain gates, and pour the great bulk of his army north through the rich Cumberland valley. If McClellan was held at bay in his efforts to take the passes, and should move north, and come down the valley, then, pointing his guns in the passes westward upon McClellan, Lee could spring like a tiger on Baltimore and Washington.
The first thing to be done after resting his army was to seize Harper's Ferry.
The people of Frederick and the farmers round the city had a chance to sell all their goods,—their boots, shoes, clothes, flour, bacon, pigs, cattle, and horses, but they were paid in Confederate money, which was worth so many rags.
Lee's army was very dirty and filthy. It had made hard marches. The men had no tents. They had slept on the ground, had lived some of the time on green corn and apples, had fought battles, had been for weeks exposed to storms, sunshine, rain, mud, and dust, with no change of clothing. They had thrown all their strength into this one grand invasion of the North, and had shown a wonderful vigor. The rest and repose, the good living which they found, were very acceptable. They obeyed General Lee's orders, and behaved well.
General Lee issued an address to the people of Maryland.
"The people of the South have seen with profound indignation their sister State deprived of every right and reduced to the condition of a conquered province.
"Believing that the people of Maryland possessed a spirit too lofty to submit to such a government, the people of the South have long wished to aid you in throwing off this foreign yoke, to enable you again to enjoy the inalienable rights of freemen," read the address.
But the people were not conscious of living under a foreign yoke, neither that they were a conquered province, and therefore did not respond to the call to rise in rebellion against the old flag.