San Francisquito Canyon Road is a two-lane mountain road that winds and dips through the Angeles National Forest, heading north out of the Santa Clara River Valley.

It's easy to drive right past the site of the worst disaster in Southern California's history.

The ruins of the St. Francis Dam are a few hundred yards from the road. Even after parking and hiking down an abandoned bit of roadway, a visitor might only notice them once they're underfoot. The huge chunks of concrete in the creek bed are overgrown and hard to distinguish from the natural contours of the canyon. Here and there, a piece of steel rebar sticks up out of the rock and the dry grass.

Eighty years ago, the St. Francis Dam stood across this canyon and held back 12 billion gallons of water.

Then suddenly it didn't.

The dam broke a few minutes before midnight on March 12, 1928. The water behind it, once destined for the bathtubs and drinking glasses of the people of Los Angeles, roared down San Francisquito Canyon and turned west along the Santa Clara River through Piru, Fillmore, Santa Paula and Saticoy before reaching the sea.

Along the way, it picked up trees, boulders, houses, livestock and people. The flood killed at least 500 people and left thousands homeless.

Lucille Matzen was part of the first wave of rescue workers. In 1928, she was Lucille Johnson, a 20-year-old Salvation Army captain in Glendale.

She was called to Santa Paula on the morning of March 13. The low-lying parts of town were devastated. Bodies floated in the river and jutted out of the mud.

Waiting out the flood

"It was such a ghastly sight," said Matzen, who lives in East Ventura now. "I'll never forget it as long as I live."

Zanada von Doeren of Oxnard was 5 years old when the dam broke, but she remembers it, too. Her parents put her in the family car, and they drove up the Conejo Grade to wait out the flood.

"We just went up there and stayed until they gave the all-clear," she said. "We were lucky; we didn't lose anything. It was the people in Santa Paula and Fillmore who lost everything."

The Ante family in Santa Paula lost almost everything. Lupe, their 11-year-old daughter, is now Lupe Simmons and lives in Ventura with her son.

She remembers her father waking her that night and leading the family out of their Seventh Street home and uphill. She doesn't remember how they found out the dam had broken.

When they walked back a few hours later, their house was gone. They had to live in a tent near the river until they could rebuild.

"There were rows and rows and rows of tents, like the ones soldiers would live in," Simmons said.

There is no single answer as to why the St. Francis Dam broke. By modern standards, its construction and materials were subpar, and the canyon floor wasn't suitable to support it.

"It was built on top of an ancient landslide," said John Nichols of Santa Paula, who wrote a book about the disaster in 2002. "It looked like a good location, because the canyon is very narrow right there, but it was unstable."

Geologists at the time, though, found no fault with the dam or its location. The city of Los Angeles built dams and aqueducts all over the state, and while there were other failures, there was never a catastrophe like the St. Francis Dam.

William Mulholland, the head of the predecessor to the Los Angeles Department of Water and Power, oversaw the design and construction of the dam and took full responsibility for its collapse. Mulholland was never the same; the father of L.A.'s modern water system retired shortly afterward and lived the rest of his life in near-seclusion.

Every five years, there's renewed interest in the disaster. The California Oil Museum in Santa Paula holds an anniversary exhibit, and the survivors again find themselves sought out by journalists and historians. There are fewer of them every time, of course. Simmons, now 91, calls herself "the last of the Mohicans."

For the third time in the past decade, Nichols is helping to put together the Oil Museum's exhibit. It opens Sunday and runs through July 27.

"It's endlessly fascinating," Nichols said. "You've got a tragedy, an engineering failure, a psychological drama as far as how it affected William Mulholland and then the heroism of how people reacted."

Nichols is fascinated by the elusive nature of heroism, and he's made it the focus of the latest exhibit.

In every town along the flood's path, people put their lives at risk to warn their neighbors of the impending disaster and help them reach higher ground. Some of those people were firefighters or police officers, but many were just ordinary citizens, Nichols said.

Monument in Santa Paula

They might not have been angels — "What if you went home after saving somebody and you kicked your dog?" Nichols pondered — but they were heroes because they rose to the occasion.

There's a monument to their deeds in downtown Santa Paula, a sculpture called "The Watchers" that depicts two motorcycle policemen who rode through town spreading the word.

There are unknown heroes, too. One woman had the grisly task of photographing all of the dead bodies at the morgue, so their families could identify them.

Her name has been lost, but Nichols' exhibit recounts her work.

"It fades in people's minds, and in some cases it fades into obscurity," he said. "Here's a significant disaster in our history, and most of the reaction I get when I tell people about it is, How come I never heard of this? Why isn't this taught in school?' I just don't know."