First Permanent Bridge Across the Mississippi: Eads Bridge, St. Louis (1874)

The Landmark

Eads Bridge (officially Illinois and St. Louis Bridge) opened July 4, 1874 in St. Louis, Missouri. It was the first permanent bridge to span the Mississippi River.

Engineering Firsts

• Steel arch design: Three spans (502, 520, 502 ft) – longest arches in the world at the time.
• Pneumatic caissons: Deepest subaqueous foundations (100+ ft below water) – pioneered by James B. Eads.
• Alloy steel: First major structure using chromium steel (supplied by Carnegie).
• Cantilever erection: Arches built outward from piers without falsework.

Impact

• Connected railroads East ↔ West; ended ferry monopoly.
• Catalyzed St. Louis as a rail hub.
• National Historic Landmark (1964); still carries MetroLink light rail & vehicles.

Earlier Attempts

Temporary pontoon bridges (Civil War), failed suspension bridge (1839). Eads was the first permanent, all-season, load-rated crossing.