6 Incredible Facts About the Bay Bridge Most People Don’t Know

The Golden Gate Bridge gets most of the spotlight. It’s iconic, photogenic, and instantly recognizable around the world.

But engineers, transportation planners, and historians often point out something surprising: the Bay Bridge may actually be the more complex and technically ambitious structure.

Here are six lesser-known facts that show why the Bay Bridge is one of the most remarkable pieces of infrastructure in the United States.

1) It Once Carried Commuter Trains for Nearly 20 Years

When the San Francisco–Oakland Bay Bridge opened in 1936, it wasn’t just built for cars.

The bridge was designed as a true multi-modal crossing:

• Cars used the upper deck
• Heavy vehicles and electric commuter trains used the lower deck

Rail systems, including the Key System, operated across the bridge until 1958.

A hidden remnant of this era still exists today. Inside the Yerba Buena Tunnel, small refuge alcoves remain along one side — spaces once used by rail workers when trains passed through the tunnel.

2) The Bridge Includes a Record-Breaking Tunnel Through an Island

Most people imagine bridges as purely above-water structures. The Bay Bridge is different.

Between San Francisco and Oakland, the bridge passes directly through Yerba Buena Island via a massive transportation tunnel. Regional planners have described it as the largest-diameter bore tunnel of its kind in the world at the time of construction.

For drivers, that means part of the bridge crossing actually takes place inside solid rock — technically inside an island.

3) The New East Span Holds Two Guinness World Records

The replacement East Span, which opened in September 2013, is more than just earthquake-resistant — it’s record-setting.

According to Guinness World Records, the East Span holds:

• The world record for the longest self-anchored suspension span
• The title of the world’s widest bridge, measuring approximately 258 feet wide

That width allows for traffic lanes, shoulders, safety features, and maintenance access — all in one structure.

4) It Was Once the Longest Bridge on Earth — and Used an Enormous Amount of Steel

At the time of its debut, the Bay Bridge was celebrated as the longest bridge in the world, a symbol of American industrial ambition during the Great Depression.

The scale of the project was staggering. Historical reporting has noted that construction consumed roughly 6 percent of the nation’s entire steel supply at the time — an almost unimaginable figure by today’s standards.

5) Treasure Island Exists Because of the Bay Bridge

Treasure Island often feels like its own strange Bay Area landmark, but it’s directly tied to Bay Bridge construction.

Material excavated during work on the bridge — including rock from the Yerba Buena Island tunnel — was used as landfill to help create Treasure Island.

In other words, part of the bridge project didn’t just connect cities — it created an entirely new island.

6) The Famous “Bay Lights” Are Expected to Return

The West Span’s “Bay Lights” installation debuted in 2013 and quickly became one of the most recognizable nighttime sights on the San Francisco waterfront.

The original installation ran for a decade before being shut down in 2023. But transportation officials say the story isn’t over.

Plans are underway for “Bay Lights 360,” an upgraded installation expected to feature 50,000 custom LED lights and wrap the entire structure in motion-based illumination. Current projections suggest a return around March 2026, pending final approvals and funding.

A Bridge That Does More Than Cross Water

While the Golden Gate Bridge may dominate postcards, the Bay Bridge quietly holds records, tunnels through islands, carried trains, created land, and continues to evolve nearly a century after it first opened.

For millions of daily commuters, it’s just part of the drive. For engineers and historians, it’s one of the most ambitious transportation projects ever built.

Did any of these Bay Bridge facts surprise you — or do you have a favorite memory tied to the bridge? Share your thoughts with readers at WaldronNews.