Final answer:
The major spike in urban growth during the mid-1800s was due to the rise in industry, facilitated by technological advances like the steam engine and a growing demand for urban workers.
Step-by-step explanation:
The major growth in cities during the mid-1800s is best described by D. the rise in industry. The industrial revolution spurred a shift from agrarian economies to industrialized ones, with factories increasingly powered by steam engines rather than water power. This technological advancement allowed factories to be located in urban areas independent of rivers, creating numerous job opportunities and drawing people to cities. Urbanization was further facilitated by technologies such as electric lighting and the telephone, as well as social factors including the influx of immigrants seeking employment and better living conditions. The resulting population boom in urban centers like New York City and Chicago was unprecedented, leading to a significant transformation in the American landscape and way of life.