sentences:  Census reports show a marked drop of nearly 10 percent in county population from 1910 to 1920, the period of the Great Migration of African Americans from rural areas of the South to northern and midwestern industrial cities offering more economic and social opportunities.Workers were recruited by northern industries, including the Pennsylvania Railroad, which was rapidly expanding at the time.As of the census of 2000, there were 12,934 people, 5,178 households, and 3,717 families residing in the county.