What Is the Statue of Liberty Made Of? Copper Skin, Iron Skeleton

The Statue of Liberty (Liberty Enlightening the World) is a masterpiece of 19th-century metallurgy and structural engineering.

Exterior: Copper Skin

• Material: 300 copper sheets, 2.37 mm (3/32") thick, totaling 62,000 kg (31 tons).
• Fabrication: Hammered into shape over wooden molds (repoussé technique) in Paris workshop of Gaget, Gauthier & Cie.
• Assembly: Sheets riveted together (300,000+ copper rivets) onto iron armature.
• Color evolution: Original reddish-brown → chocolate brown (10–20 yrs) → green patina (verdigris, copper carbonate/sulfate) by ~1906. Patina protects underlying copper.

Interior: Iron/Steel Framework

• Designer: Alexandre-Gustave Eiffel (yes, that Eiffel) with Maurice Koechlin.
• Structure: 1,800 kg central pylon (four iron posts) + secondary trusses + 300+ "saddle" brackets holding copper skin.
• Innovation: Flexible connection allows skin to expand/contract thermally and sway in wind (up to 7.5 cm at torch) without stress.
• Material: Puddled iron (low-carbon, pre-steel); later reinforcements: stainless steel (1980s restoration).

Other Materials

• Torch: Original copper (1886) replaced 1986 with gold-leafed copper; original in museum.
• Pedestal: Concrete faced with granite (Fort Wood). Richard Morris Hunt design.
• Foundation: Concrete mass on bedrock.

Dimensions

• Height (heel to torch): 46 m (151 ft)
• Total (with pedestal): 93 m (305 ft)
• Weight: 225 tons (statue), 27,000 tons (pedestal+foundation)

A thin copper shell on an iron skeleton—light, flexible, enduring. The green lady is a materials science triumph.