sentences:  With coal underlying the entire region, the most economical development was to place mines alongside the railroad tracks (for transportation of coal), and located in or near already-existing towns.By the twentieth century, there were mines in many towns, all of them with substantial populations of foreign-born miners from everywhere in Europe.During the twentieth century, agriculture and coal mining remained the mainstays of the county's economy, and the county's fortunes rose and fell with them.