How did the increase of textile mills and factories in the north affect the population in the south in the period from 1820 to 1850? as more americans moved to the north to find jobs, the population in the southern states began to decrease. because cotton was a necessity in the textile mills, the population of americans who owned slaves increased dramatically. the population of farmers growing cotton and grain crops increased dramatically, while those growing sugar and tobacco decreased. the demand for southern products like cotton increased, so the southern population grew rapidly.