Final answer:
The U.S. population changed in the early to mid-19th century primarily due to a large influx of immigrants coming to the country. This wave of immigration resulted in a rapid increase in population and led to urbanization. The population growth was also influenced by demographic, economic, and political factors, as well as the push for westward expansion.
Step-by-step explanation:
The U.S. population changed in the early to mid-19th century primarily due to a large influx of immigrants coming to the country. This wave of immigration resulted in a rapid increase in population from about five million to over twenty million in a fifty-year period. The immigrants came for a variety of reasons, including seeking work in America's growing industries and opportunities for a better life. The population growth was also influenced by demographic, economic, and political pressures, as well as the push for westward expansion.
During this time, cities experienced significant urbanization as immigrants and workers settled near industrial areas where they could find employment. These new technologies of the time, such as electric lights and powerful machinery, contributed to the industrialization and required a large workforce. The urbanization and population growth led to challenges and opportunities in the major cities, as depicted in the Figure 19.3.
In conclusion, the U.S. population changed in the early to mid-19th century primarily due to the arrival of large numbers of immigrants. This influx of immigrants, along with the push for westward expansion and industrialization, resulted in a significant growth in population and urbanization.