...e while the investment of Harper's Ferry was being completed. Marching with Longstreet on the 10th, Lee crossed the South mountain to Boonsboro, where, learning that a Federal force was threatening Hagerstown from the direction of Harrisburg, he proceeded to that point, and there placed Longstreet in bivouac on the evening of the 11th, on which day D. H. Hill crossed the South mountain, but still holding ...