Porn Valley- PORNOGRAPHY is as old as time. But Los Angeles is the place that turned smut into gold.

Inside faceless office buildings on Ventura Boulevard and tract houses in Woodland Hills, Angelenos have spent the last two decades transforming an underground world into a multibillion-dollar industry.

You can catch an early glimpse in Russ Meyer’s breast-laden flicks from the late 1950s and early 1960s – which often featured Southern California as the background to their wild-woman antics. But while they were skeezy and flesh-focused, they were still soft core.

Things started to get down and dirty in the late 1960s, when John Holmes was discovered at a Sunset Boulevard casting call. In 1972 and 1973, three hard-core porn movies – “Behind the Green Door,” [shot in San Francisco] “The Devil in Miss Jones” [shot in NY] and the groundbreaking “Deep Throat”,www.xxxdeepthroat.com [shot in Miami]- took the United States by storm. “Deep Throat” became the highest-grossing picture in Los Angeles, and adult producers took note.

Still, adult entertainment remained an underworld commodity into the 1980s. Adult performers and producers would meet at supermarket parking lots in the Valley, pile into vans and drive off to warehouses to film on the fly.

Things started to change when Vivid Video entered the picture in 1985. Founder Steven Hirsch revolutionized the business by putting actress Ginger Lynn under contract and giving her the star treatment. Porn became a designer commodity, as brushed and beautiful as a Guess jeans ad.

Theories abound about why the San Fernando Valley is now the San Pornando Valley – sun, proximity to Hollywood, more than your average number of beautiful blond women looking for work. But there’s no question why Los Angeles became ground zero for the industry. It all boils down to a single court case, the people vs. Harold Freeman.

Freeman was arrested in Van Nuys in 1983 after he hired five women to perform sex acts for a film. He was convicted of violating the state’s “anti-pimp” law, with prosecutors saying the women were effectively serving as prostitutes.

In 1988, though, the California Supreme Court ruled on appeal that a producer could hire actors and actresses to perform sexual acts as long as it was for a film.

The court found no evidence that Freeman had paid “for the purpose of sexual arousal or gratification, his own or the actors.’ “

Rather, he hired the performers to make a movie, an act protected by the 1st Amendment. With this as a guiding principle – that it was a matter of business, not pleasure – California legalized porn production.

Buoyed by the VCR revolution, the industry took off. Today, thanks to the Internet, porn is available everywhere you want, whenever you want. Estimates put the number of porn films produced in 2006 at close to 15,000, many of them shot in Encino and Chatsworth.

Meanwhile, porn stars such as Jenna Jameson, whose autobiography made the New York Times bestseller list, have pushed adult entertainment into the mainstream in places as far-flung as Buffalo, Moscow and Shanghai.

The aesthetic of the Valley’s sex films – hairless, tan and raunchy – has rippled through every aspect of American entertainment, fashion and recreation, down to the pole-dancing class at the gym.

What more could porn’s producers want? Now they can do their business out in the open, meeting in glass office buildings to apply for film permits while actresses file letters of incorporation, making their wax jobs tax-deductible. And the sun blazes down on their endeavors, all across the world.