Tacoma Narrows Bridge

Listen first. Below the deck, the water of the Narrows moves fast and green-grey. Above you, steel cables hum faintly in the wind that pushes through this gap in the hills. The air smells of salt and cold fir. Two green suspension bridges stand side by side here, almost like twins. Each one carries the weight of a story that began with a spectacular failure.

You are standing above the Tacoma Narrows, a tight strait of Puget Sound. Here the water squeezes between Tacoma on the east shore and the Kitsap Peninsula on the west. When the tide turns, enormous volumes of seawater pour through this channel. The currents are strong, and the wind follows the same corridor. For engineers, that combination of deep water, fast currents, and steady wind has always made this a difficult place to build.

For generations, people crossed here by ferry. Communities like Gig Harbor on the far side felt cut off from the city. A bridge promised to change that. In the late 1930s, construction began on a long, slender suspension bridge. It opened to traffic on July 1, 1940. At the time, its central span ranked among the longest in the world. It was also strikingly thin — a narrow, graceful ribbon of road hung between two towers.

That thinness was the point. The design came from Leon Moisseiff, a respected engineer who believed suspension bridges could be lighter and more elegant. Instead of a deep, open steel truss under the road, this bridge used shallow, solid plate girders. It looked modern and clean. It also had a habit that nobody had planned for. Even in moderate wind, the road deck rose and fell in visible waves.

The construction workers noticed this movement before the bridge even opened. Drivers soon noticed it too. People gave the bridge a nickname — Galloping Gertie. Some motorists came just for the ride. They said cars ahead of them would disappear into a dip, then rise again, as if on a slow roller coaster. Engineers studied the motion and tried to calm it with cables and other fixes. Nothing worked for long.

Then came the morning of November 7, 1940. A steady wind blew through the Narrows. The bridge began to move differently. Instead of only rising and falling, the deck started to twist. One side lifted while the other side dropped. The road surface rolled like a wringing towel. The bridge was closed to traffic. A few people were still out on the deck, and they struggled back to the shore on foot.

One of them was a newspaper man named Leonard Coatsworth. He had driven onto the bridge with his daughter's dog, a cocker spaniel named Tubby, in the car. As the deck began to twist, Coatsworth abandoned the car and crawled to safety. An attempt was made to rescue the dog, but the frightened animal would not leave the car. Tubby was the only life lost that day. No people died.

Here is the first detail many visitors miss. The collapse was filmed. Local camera shop owners and a university engineering professor captured the twisting deck on film. The footage shows the centre span tearing loose and falling into the water below. That film became one of the most watched pieces of engineering footage in history. Physics and engineering students around the world still study it today.

And here is the second surprise. Many textbooks once described the collapse as simple resonance — the wind matching the bridge's natural rhythm, like a singer breaking a glass. Engineers today explain it differently. The main cause was a process called aeroelastic flutter. In plain terms, the twisting motion of the deck changed how the wind pushed on it. That push fed more energy into the twisting, and the motion kept growing until the structure failed.

The lessons from Galloping Gertie changed bridge design everywhere. Engineers began testing models in wind tunnels before building. They paid much closer attention to the shape of a bridge deck and how air flows around it. The replacement bridge here was built with a deep, open steel truss under the roadway. The open design lets the wind pass through instead of pushing against a solid wall. That bridge opened in 1950 and still carries westbound traffic today.

Traffic kept growing, and by the early twenty-first century one bridge was not enough. A second suspension bridge was built beside the first. It opened in 2007 and carries eastbound traffic toward Tacoma. Look at the two bridges together, and you can see more than half a century of engineering side by side. The towers and cables look similar, but the details belong to different eras of design and construction.

Below the surface, the old bridge is still here. The wreckage of the 1940 span lies on the floor of the Narrows. Over the decades it has become an artificial reef, home to marine life such as octopus and fish. The site is listed on the National Register of Historic Places. The strong currents make it a challenging place to dive, so only experienced divers visit it.

Now, take a moment where you are. Watch the water moving under the bridges, and notice how quickly it travels. Feel the wind on your face, and look up at the cables rising toward the towers. Every car crossing here travels on a structure shaped by one November morning in 1940. As you leave, look back once more at the two green spans. They stand steady in the same wind that once brought a bridge down.