There’s a fire truck on that roof!

Drive through the industrial town of Vernon and the streets are lined with low-slung commercial buildings housing factories, shipping businesses, massive refrigeration units and warehouses.

But turn onto Vernon Avenue and the gray commercial street scape suddenly changes. Atop the three-story Red Chamber Co. building sits a red fire engine -- strapped and bolted to the roof.

The fire engine, built in 1948 by General-Detroit Corp., has been there for years, but its origin has been one of Vernon’s great architectural mysteries.

“I don’t know how it came out to be up there. It’s pretty unusual, kinda neat and beautiful, but what’s it doing up there?” said Assistant Fire Chief Mike Wilson of the Vernon Fire Department.

For people who work near the truck, there are many theories. Some say the building used to be a museum and that the truck is the last remnant.

Others believe it’s some sort of tribute to the Fire Department.

But look closely at the writing on the passenger side of the truck, and it reveals a key clue.

“Town of Harmony / Engine No. 1 / And only.”

Harmony, Calif., is 200 miles north of Los Angeles, in San Luis Obispo County. The town, with a population of 18, is just off California 1 along the coast.

The town is made up of a cluster of buildings that sit along Old Creamery Road. There is one post office -- which has not provided postal service in two years -- two homes, pottery and glasswork shops and a wedding chapel with a banquet room.

“It’s a nice and peaceful place,” said Emily Dobie, who works at Harmony Pottery. “It’s fun to watch people who’ve never been here before.”

Harmony was founded in 1869 around a creamery in an area that was referred to as Harmony Valley. In 1907, a local dairyman, Marius Salmina, and his brother took over the creamery. Salmina campaigned for a cooperative and successfully established the Harmony Valley Creamery Assn. with 20 other dairymen. The town’s success is linked to Salmina and the establishment of that cooperative.

But hard times befell Harmony, and the town all but disappeared for a while.

Restoration of the small community began in the 1970s when Ralph Casper and Paul Fields purchased it. The pair transformed the hamlet into an arts community. The town eventually was sold to George Mayers, a Beverly Hills contractor, for $375,000. His plans were to continue restoration of the town.

In 1981, Mayers sold Harmony to Jim and Kay Lawrence for $650,000.

But he wanted a souvenir of his time as Harmony’s owner.

So Mayers brought the town’s fire engine to Vernon, according to interviews with Vernon officials and the Vernon Industrial Digest.

In 1987 he hoisted the truck to the roof of his company’s headquarters, at 1912 E. Vernon Ave., using a 100-ton crane. The following year, he brought an old New York Central railroad dining car and placed it on the side of the building’s parking lot, according to city documents.

For more than 20 years the fire truck has sat on the roof, its wheels strapped down to large wooden beams that are bolted to the roof. The dashboard has collected dust, and the springs of the driver and passenger seats are exposed and rusted.

It remained even after Mayers sold the building to its current owner, Ming Kou, who runs the Red Chamber Co., a seafood business.

Kou said he never thought about taking down the fire engine, saying he thought it gave his building distinction.

“It makes a great conversation starter for our out-of-state and international customers,” Kou said.

A day after the Sept. 11 attacks, a flagpole with an American flag was welded to the railing next to the truck. Employees occasionally climb up to change the flag whenever it becomes old or torn.

Kou also kept the dining car. It’s currently being used as a storage room, he said, but he hopes to use it as a lounge room for his employees and guests one day.

“We just haven’t got around to it,” Kou said.

The fire truck continues to keep people in Vernon guessing.

“I’ve always wondered how it got up there,” said Walter Henderson, 53, a bus driver.

“I thought it had to do something with a fire station, but apparently not.”

Selling bags of mangoes nearby, Hilario Bautista, 43, said he also thought el camion, “the truck,” had something to do with a fire station.

“I guess it’s there for decoration,” he said.

Howard Choi, the controller of Red Chamber Co., said, “We’re going to keep it as long as we can. We’ll keep it forever, well as long as we have the property.”

ruben.vives@latimes.com