When director Howard Ziehm made Harlot, in the late summer/early fall of 1970, feature length hardcore movies were still in their infancy, and inherently radical.
Ziehm, who dismissed the pretense of writing off his hardcore movies as 'art' films rather than 'fuck' films, had, nevertheless, developed a rather auteurist approach to his early movies, that of in your face rebellion against accepted regulations of 'decency' and 'morality.'
In MONA, Ziehm toyed with sexual hypocrisies with his comedic story of a young woman who refuses to have sex before her wedding day, but is quite content to give strangers blowjobs. The commentary, though pervasive, was really little more than an amusing way to move the film from one sex scene to the next. In HARLOT, however, Ziehm constructed an entire film around presenting sexuality in a way that, quite literally, threw it in your face.
Once again, the story is simple and rather uninvolved: two high school friends, one proper and innocent, the other perpetually horny and with a penchant for picking up and fucking strangers, embark on a series of sexual mid-adventures with various LA weirdos, however the at first wholesome girl quickly learns to embrace her sexual freedom, going further than even her friend would dare.
HARLOT is aggressive in its radicalisms, both in the types of sex it depicts, much of it focused on high school girls, but in how and where it happens. While most early hardcore features of the same era restricted their explicit couplings to bedrooms, couches, and the odd table, Ziehm presents every single sex scene in a public place. From the mundane (a bathroom and office), to the absurd (moving cars and an elevator), to the sublime (atop a Hollywood skyscraper and on a beach), but with each such sequence serving to further his basic agenda, that sex is everywhere, unstoppable, and deservedly out in the open. 
The film's most famous shot, and still among the finest cinematic achievements in the history of hardcore features, is a helicopter shot over the Hollywood skyline which eventually focuses in on the roof of The First Federal Building, where a three-way is taking place. It's a remarkable scene and one can only imagine the splendid shock of seeing it on the big screen for the first time, back when the film premiered in early March of 1971. Without intending to, Ziehm encapsulates the entire ideology of the 'free love' movement in this one short moment; that sexuality is no longer to be hidden away in bedrooms in the dark of night, but is free to be enjoyed anywhere and everywhere, including the roofs of buildings for all to see.
While Ziehm was the architect of HARLOT; he wrote, directed, and photographed it, his creative partner at the time, Michael Benveniste, who edited the film, took Ziehm's visuals and assembled them into an increasingly avant garde manner that, as the film progresses, feels more like a free flowing piece of self-reflective cinematic experimentation than the latest attraction for the Pussycat Theatre. The film's final 15 minutes veer into full on absurdity, with impeccable usages of slow motion, color bleed outs, and the film's second most radical shot, a slow motion streaking scene through a crowded shopping plaza.
Now, over 45 years later, looking at HARLOT may not hold the same level of wide eyed amazement as it did in an era where, laws of public indecency aside, its director and cast could have been jailed for years for even making a sexually explicit film, but as the 21st century has become a time for faux liberal neo-conservatism which privileges marriage over free love and prudishness and monogamy have become the championed 'liberated' lifestyles, watching HARLOT through a modern lens makes it more relevant than ever, perhaps because it's a reflection of a time when people wanted to explore, confront, and challenge others' views on the 'proper' place for sex, rather than rigidly compartmentalize all sexual desires out of fear of offending someone. In this regard, HARLOT becomes more than an artistic and sexual time capsule of how things were, it's a stone cold reminder of how they will probably never be again.