This Chapter examines the demographic and capital formation dynamics that underpinned South Korea’s rapid economic growth and its catch-up with advanced economies such as the United States and Japan. The analysis begins by exploring Korea’s demographic transition, highlighting key shifts in population composition, such as declining dependency ratios, and their impact on economic development at various stages. Human capital formation is assessed through the expansion of formal education and workplace skill development via training and experience. The chapter also investigates workforce changes, analyzing shifts in industrial and occupational composition before and after liberation, and traces long-term trends in per capita productivity. In the realm of physical capital, it reviews the development of transportation and communication infrastructure and examines East Asia’s exceptionally high investment and savings rates. The chapter concludes by identifying the factors that facilitated Korea’s robust capital accumulation, a cornerstone of its sustained growth.