Which innovative construction product, first patented in 1867 but not widely used until the early 20th century, enabled the dramatic rise of skyscrapers and modernist architecture?

In the world of architecture, certain product innovations have fundamentally transformed how buildings are designed and constructed. This trivia question focuses on a game-changing product innovation that revolutionized architectural possibilities in the 20th century. Test your knowledge of architectural history and the materials that made modern landmark buildings possible!

This is a live public trivia poll on AIPolls.Net. Vote and see real-time results.

Reinforced concrete (steel rebar embedded in concrete)
Plate glass manufacturing process
Aluminum extrusion technology
Curtain wall systems