Final answer:
The South's progress lagged behind the North's due to its traditional, agrarian society focused on slavery-dependent plantation agriculture and a lack of industrial development, which impeded economic and infrastructural advances and stifled social mobility.
Step-by-step explanation:
The South fell behind the North in terms of progress primarily due to its societal structure and economic dependence on slavery. The Southern society was traditional, predominantly agrarian, and based on large-scale plantation-style agriculture, where the rigid, race-based class system prevailed. This reliance on slavery and plantations meant that there was less industrial development compared to the North, leading to a lack of industrial capabilities and infrastructure such as railroads for efficient mobilization and supply. Moreover, the South lacked a significant industrial, middle class and had fewer immigrants seeking employment, partly due to poor soils and the absence of a relevant source of industrial energy for widespread industrialization.
In the antebellum South, the male-dominated society with patriarchal figures in control left little room for social mobility, and gender roles were strictly enforced, which stifled progress. The institution of slavery denied all laborers, slave and free, the dignity and social mobility that might drive economic development. The North's concerns about the free labor system reflect this economic disparity, as they saw slavery leading to mass poverty among whites and a lack of the qualities that fuel progress, such as hard work and industry. Moreover, the industrial capacity and population of the North far exceeded that of the South, with more people working in factories and producing industrial goods, which also constituted an advantage in supplying the military.