Between 1880 and 1900, cities in the United States grew at a dramatic rate. Owing most of their population growth to the expansion of industry, U.S. cities grew by about 15 million people in the two decades before 1900. Many of those who helped account for the population growth of cities were immigrants arriving from around the world. A steady stream of people from rural America also migrated to the cities during this period. Between 1880 and 1890, almost 40 percent of the townships in the United States lost population because of migration.