Final answer:
The rise of full-time police departments in America was influenced by the industrialization and urban growth of the late 19th and early 20th centuries, as well as the bureaucratic expansion periods of the 1930s and the 1960s, which included the end of Prohibition and the civil rights movement.
Step-by-step explanation:
The rise of unified, full-time police departments in America was significantly influenced by a number of societal changes, which took place during the late 19th and early 20th centuries—a period marked by industrialization and urban growth. This period saw an increase in the population and economic size of the country, resulting in increased urbanization and the creation of a more central federal government involved in infrastructure projects like railways. Additionally, the early 20th century's Progressive Era aimed to combat urban vice and improve living conditions, leading to the establishment of a more organised approach to law enforcement.
Two later periods of large-scale bureaucratic expansion that are noteworthy include the 1930s and the 1960s, both of which were times of significant social and political change. The period of the 1930s saw the end of Prohibition and the recovery from World War I, and the 1960s was the peak of the civil rights movement, which also led to changes in policing and criminal justice policies. Such changes in different periods, characterized by intense social upheaval or major shifts in public policies, have shaped the modern policing system in the United States.