Why did some Americans consider urbanization a threat to the nation's political system?

Although Americans were moving to cities in ever greater numbers, they also saw the city as a source of several social problems. Because the countryside had traditionally been considered the source of America's uniqueness, many Americans feared that the growth of cities posed a serious threat to their nation. Nineteenth-century cities grew rapidly, and so often lacked adequate sanitation, housing, and other necessities. Because cities were home to many of the immigrants arriving in the U.S., some native-born Americans worried that cities were home to millions of people unfamiliar with American institutions. They charged that cities were run by corrupt political machines, which exchanged political favors for immigrant votes. The most notorious of these machines was in New York City, where the Democratic party machine, known as Tammany Hall, dominated the city for decades. As Henry George, one of the leading American economists of the late nineteenth century, wrote ominously in 1879, "The new barbarians are gathering strength in the squalid quarters of our great cities."