Complex sentence: From that base some went south into Virginia, the Carolinas and across the South, with a large concentration in the Appalachian region; others headed west to western Pennsylvania, Ohio, Indiana, and the Midwest.
Split into simpler sentences: From that base some went south into Virginia, the Carolinas and across the South, with a large concentration in the Appalachian region. Others headed west to western Pennsylvania, Ohio, Indiana, and the Midwest.