Final answer:
Electric trolleys and advancements in transportation allowed for the development of streetcar suburbs, segregating cities by class and facilitating suburbanization. This created socio-economic divisions as the middle-class moved to suburbs with better amenities while urban centers remained crowded and less serviced.
Step-by-step explanation:
The trolleys began to divide cities by class at the end of the 19th century due to the development of transportation that allowed for greater mobility. With the invention of the electric trolley by Frank Sprague in 1887, people could live farther from their work as long as they were close to a trolley line. This led to the creation of streetcar suburbs, where middle-class families could reside away from the crowded city centers. These suburbs were often segregated by ethnicity and race, creating a clear division in urban living conditions.
As transportation continued to evolve, with the introduction of elevated trains and subways, the segregation between the classes became more pronounced. This infrastructure facilitated the creation of districts specialized for manufacturing, finance, shopping, and even vice. Those with the means could purchase homes in the suburbs, enjoying advantages such as parks, plumbing, and electricity—luxuries not available to the majority of urban dwellers living in cramped tenements.
The trend of suburbanization continued into the 20th century with the advent of the automobile, which allowed people to live even further from the city core, exacerbating urban decentralization. Thus, the advancements in transportation technology and infrastructure were directly linked to the deepening of socio-economic divisions within cities, shaping living patterns for decades to come.