Lecture 12 traces the evolution of skyscrapers from their origins in the Chicago School to their widespread adoption in New York and other global cities. The lecture explains the key technological, structural, and urban preconditions that enabled tall buildings, including steel-frame construction, passenger elevators, fireproofing, grid-iron planning, floating foundations, and standardization. It examines how architects like Louis Sullivan addressed the aesthetic problem of height through principles such as “form follows function.” The lecture also discusses the impact of early skyscrapers like the Equitable Building, the resulting 1916 Zoning Resolution, and the emergence of setback (wedding-cake) skyscrapers, leading to Art Deco expressions and shaping modern urban skylines.