Steve Apostolof had a frown on his face as he drove past Happy Face Hill.
The hillside features a 150-foot-wide smiley face that was created in 1998 by a man armed with a weed-whacker and a sprayer of herbicide. Since then, it has become something of a curiosity piece that welcomes motorists on the 118 Freeway to Simi Valley.
But in the January dusk, Apostolof couldn't see Happy Face Hill, let alone its enormous grin.
"With the sun setting early, the hill was pitch-black," Apostolof said of his trip home from work.
The next night, Apostolof dug around in his garage for a set of solar lights and took them to the hill just west of Kuehner Drive. But they were too dim to do the job.
So Apostolof, who operates a pizza restaurant in Chatsworth, went out and bought $100 worth of brighter solar lights, recruited some friends and illuminated Happy Face Hill. He calculated that it could be seen from half a mile away, at least.
As the days have passed, smaller solar lamps have been added, giving the face even more sparkle.
Northridge gardener Sonny Klamerus said he was stunned when he saw that someone had improved on his creation.
"Wow. That's a surprise to me," said Klamerus, 63. "I haven't been out there for a while."
Klamerus created the Simi Valley smiley face after considering carving it on hillsides in Granada Hills and Porter Ranch. But those slopes were too far from the freeway for motorists to clearly see the grin, he determined.
When the smiley face finally appeared off the 118, its creator was a mystery. "Nobody knew who was doing it for many years," said Jim Purtee, Simi Valley's assistant city manager.
Klamerus acknowledges that he trespassed on the hill to create and maintain the grinning face. Later, he obtained permission to enter the site from the development company that owned it.
"I wanted to do a benign, nice thing. It wasn't meant to be political. I just eyeballed it when I was drawing the face," he said. "I screwed up one of the eyes — it was lower than the other one."
One day he noticed that someone had draped a sheet across some brush to make it appear that a cigarette was hanging from the mouth of the smiley face.
"I climbed up the hill and pulled the sheet off," he said.
The property has changed hands several times and the area next to the hill is now marked to be developed with 66 town houses, said Paul Drury, a Simi Valley city planner. The new units will not obscure the grinning symbol, he promised.
Over the years, the smiley face has been scorched by a wildfire and often becomes overgrown with brush, which Klamerus or other volunteers carefully cut away. On the west side of Happy Face Hill, Klamerus has carved a giant valentine.
The hillside grin has also gotten its own Facebook page, which has been "liked" nearly 7,000 times, according to page creator Brian Dennert, a world history teacher at Simi Valley's Royal High School.
Dennert said he uses Happy Face Hill in his classroom as an example of how things can help define a sense of place.
"It's become a cultural landmark, one that is important to young people who go off to college and then come back to Simi Valley," he said.
Klamerus said photos of the lighted symbol indicate that his original design has been altered — the face has been moved and its grin has been altered. He's not smiling about that, he admitted.
That change apparently occurred later in January when the local Sunrise Rotary Club helped tidy up Happy Face Hill.
Apostolof said he didn't outline the face's circle with smaller garden lights, either. The source of those remains a mystery, he said.
"But that face cracks me up every time I see it," Apostolof said.
Day and night.