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Treasure Island is man-made, engineered with bay mud on a shoal adjacent to naturally occurring Yerba Buena. San Francisco History Center/San Francisco Public Library
Treasure Island is man-made, engineered with bay mud on a shoal adjacent to naturally occurring Yerba Buena. (San Francisco History Center/San Francisco Public Library)

How Treasure Island Got Made — and Why

How Treasure Island Got Made — and Why

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This is part 1 of a two-part series on Treasure Island. Part 2 explores the future of Treasure Island.


ave you ever visited Treasure Island? The low-lying island that humans made from mud and rock on a shoal in the middle of San Francisco Bay?

Bay Curious listener Gary Pilgram stopped there during a romantic drive across the Bay Bridge with his wife. Enchanted by the panoramic view of the Bay Area, Gary wondered: What’s the island’s past?

An aerial photo of Treasure Island from 2015.
An aerial photo of Treasure Island from 2015. (Josh Edelson/Getty Images Stringer)

Origin Story

In the 1930s, passenger flights were gaining popularity, and San Francisco’s airfield, Mills Field, couldn’t accommodate the demand. The city needed space for a larger airport and was on the hunt for land.

At the same time, engineers were almost done building both the Bay Bridge and the Golden Gate Bridge, which would open within a year of each other. The city wanted to celebrate these engineering marvels with a big world’s fair.

They had held two fairs before: the California Midwinter International Exposition of 1894 in Golden Gate Park and the Panama-Pacific International Exposition in 1915.

Both fairs were successful, says Anne Schnoebelen, historian and member of the Treasure Island Museum’s board of directors. Leaders were ready to host another as the city emerged from the Great Depression.

“City leaders said, ‘We know how to do a world’s fair. This depression isn’t going to last forever, we need something to look forward to. Let’s have a new world’s fair in San Francisco. What do you know? They decided they wanted to do it on Yerba Buena shoals,” Schnoebelen says.

Federal Money

Of course, San Francisco needed money to build the island. City leaders pitched President Franklin Roosevelt on the idea.

“FDR really loved the idea of an airport and was agreeable to the idea of a world’s fair,” she says. “The federal government provided quite a bit of money to build the island.”

The Army Corps of Engineers piled hundreds of thousands of tons of boulders onto the the shoals north of Yerba Buena Island. They dug up the equivalent of 2½ million dump trucks of bay mud and sand, dumping the muck inside the boulder dam.

The Army Corps of Engineers dredged up the equivalent of 2½ million dump trucks of bay mud and sand to construct Treasure Island. (San Francisco History Center/San Francisco Public Library)

All the while, the president’s focus was on World War II.

“The military development of the Bay Area was a very big thing in the ’30s,” Schnoebelen says.  “And Treasure Island was part of that big buildup.”

While city leaders focused on the fair, she says that FDR wanted to make sure the island had a submarine turning basin.

From the beginning, Treasure Island was the site of a tension between something romantic — a world’s fair to celebrate the city’s achievements — and the powerful, overwhelming force of World War II.

The Fair

The Golden Gate International Exposition opened Feb. 18, 1939.

“People were so excited that the fair’s promoters cautioned people, saying, ‘Well, you better not come on opening day. It’s going to be too busy,’ ” Schnoebelen says.

On the first day, more than 150,000 people descended on Treasure Island. California’s governor opened the gates with a jewel-encrusted key, reportedly worth $35,000.


There were art deco towers, sprawling gardens and sculptures. Schnoebelen says the fair celebrated extravagance.

“It was a big theatrical presentation with incredible lighting,” she says. “Purples and aquas and bright orange and gold. At night, it must have really been something to see.”

She says people could visit ornate buildings like the “Temples of the East” and the “Court of Pacifica” that were an “effort to make the fair look like what its subtitle was, which was ‘the Pageant of the Pacific.’ ”

An image of the 1939 World’s Fair taken from afar. (Max Kirkeberg Collection/San Francisco State University DIVA Commons)

With Europe already at war, and tensions rising between Japan and the U.S., the fair’s organizers wanted to send a message of unity and peace. They included architecture from across the Pacific.

“But really, it was just a big movie set,” Schnoebelen says.

The Island’s Next Phase

The fair ended in September 1940. The war in Europe was impossible to ignore and the Navy soon began occupying Treasure Island.

“I understand, they basically started moving onto the island almost as soon as the fair ended,” Schnoebelen says.

On the island, the Navy registered sailors and prepared them for deployment. All together, more than 4.5 million soldiers stopped at Treasure Island before deploying to the war.

Instead of San Francisco’s airport, as was the original plan, the land became Naval Station Treasure Island. It remained a naval station until the 1990s.

The Future

Soon, the island will undergo another makeover as thousands of new homes are built. But as the bay waters rise, uncertainties exist.

Read Part 2: The Precarious Future of Treasure Island: Rising Seas and Sinking Land


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