Sheila McClear, 30, was a college-educated girl from Michigan who came to New York in 2006, full of ambition. But despite her best efforts, she couldn’t find a job — and drifted into working for the peep shows in Midtown. Now a writer for the New York Post and the author of the forthcoming “The Last of the Live Nude Girls,” McClear tells the story of how she got from there to here.

I grew up in a small town, surrounded by cornfields, in a conservative household 20 miles outside of Flint, Mich. I attended both Catholic and Baptist churches. When I was a senior in high school, I had an 11 p.m. curfew, and my parents only allowed me to date — grudgingly — when I was 17. I was a late bloomer (I didn’t lose my virginity until I was almost 22), terribly uncomfortable with myself and painfully shy.

I went to college at the University of Michigan in Ann Arbor, where I studied costume design. While my fellow students were exploring their newfound freedom by partying, experimenting with drugs and sleeping around, I did none of these things.

Ever since I was a kid, I felt drawn to New York City.

I started reading the New Yorker when I was 12, and in college, I always kept up with what was happening in the city through magazines and media. After I graduated, I wanted to move to the Big Apple, but I couldn’t afford it, so I took a job as a reporter in Detroit until, one day, I read a review of a play in The New Yorker — and wrote a letter to the theater asking for a job.

One day, the costume designer called and offered me a chance to work backstage. I couldn’t believe it was that easy, even if the pay was only $125 a week for a two-month run.

When the play’s run ended, my savings were almost gone and I had to scramble for a new job. I was living in a flophouse on 99th and Broadway, and I could barely pay the $20-a-night rent.

I knew I ultimately wanted to be a writer, but right then it was all about day-to-day survival. I went on at least two dozen interviews to be a waitress or a hostess, but everyone wanted at least two years “New York experience” and a head shot.

I signed up at eight temp agencies, which got me nowhere.

Like many college grads, I actually had very few marketable skills.

I had never properly learned Excel, or PowerPoint, or Photoshop. I applied to make coffee at Starbucks, sell clothes at American Apparel and bake cupcakes at Magnolia Bakery. No one called. I worked the door at the Webster Hall nightclub for one night, and one night only, before the manager told me he’d pay me during my next shift but never called to give me another one.

In New York, I learned, you needed an “in.”

I had a half-dozen college friends scattered across the five boroughs, but they were all struggling to get by, as well.

I had no ins.

Moving home wasn’t an option; I never even thought about it.

Eventually, I found a job telemarketing in a windowless room in Battery Park City for $12 an hour, where the boss paid us by personal check — if and when he felt like it. I was let go after less than a month, halfway through my shift, for failing to meet the quota. He’d been weeding out the weak and inefficient all week, and he was right to get rid of me; I was not very good at the job.

By any reasonable standard, I was beginning to lose it.

Walking aimlessly down Eighth Avenue one afternoon on my way to apply for a job at the bar Latitude, I saw a neon sign advertising “LIVE GIRLS.” Underneath was a porn store called Gotham City Video, sandwiched between the bar and the headquarters of Gray Line Bus Tours.

I was fascinated by the honky-tonk idea of an actual peep show, hardly believing that they still existed. I imagined that the girls dressed up in pinup-style showgirl costumes every night. I walked in. Suddenly, I thought that throwing myself into the most extreme situation possible would shock me out of being the small-town hick I’d always felt like.

Under harsh fluorescent lighting showcasing a wall of sex toys, I asked the stern man behind the counter, wearing the store’s uniform bright yellow vests, if they were hiring girls. It was July, and I was sweating, my hair stuck to the sides of my face.

He looked me up and down. “You have ID?”

I handed him my passport.

“Fill out paperwork and put your name on the schedule,” he barked. I signed up for the ominous-sounding graveyard shift under the name “Chelsea,” which seemed as good a stage name as any; it had a nice girl-next-door ring to it. I told myself I probably wouldn’t show up.

But two weeks later, bleeding money, I walked in for a shift.

Soon enough, I had a black bobbed wig, a pair of cheap plastic stilettos and a booth of my own. I was 25 and had been living in New York for six months, and I was working in a peep show.

I had a somewhat innocent idea about what went on at the peep shows.

What I didn’t realize was how dark that world would be.

As a peep-show girl, my survival was based on hustling, convincing the neon-overdosed tourists, curious college boys, Mexican laborers and guilt-ridden street preachers — plus the natives, the sundry damaged goods of Times Square — to pay $35 to watch me take my clothes off, with the bare minimum of enthusiasm, behind glass. They stooped and genuflected to put money through the slot sawed into the red-painted booth.

To start a show, a man slid $10 into the bill reader, and a black plastic curtain ascended. It moved slowly, presenting the girl on the other side little by little, its motor wheezing and whirring as it struggled to raise itself yet again. When the show was over, the curtain went down just as slowly. Sometimes I waved farewell as the man on the other side of me disappeared from view. Sometimes the men panicked, reaching toward the glass, bending or kneeling to catch every last glimpse before I was gone.

All night, men came in off the street and told me things. They were always alone, wandering Times Square as if they were searching for something. They shamelessly bargained and asked us if we “did sex.”

“Two hundred dollars,” they’d repeat over and over in foreign accents, unblinking, until I laughed or sighed or tried not to scream. We “live girls” told the men the show was five minutes long, but the curtain went down after 31/2. A bored Southern salesman chewed a toothpick while watching me.

Once, a customer who told me he was a reporter at the Daily News asked me what I really wanted to do with my life — and what was I was doing in a place like this?

It was complicated. I was trying to get a foothold in New York, and I was also trying to figure out some of the deeper, tangled parts of myself. I had chosen to figure out how to express my sexuality in what seemed like a safe way: protected behind glass.

I could make $300 or $400 in a night, if I was lucky. Not every night was so good, but it was a lot of cash for a six-hour shift. Plus, it meant I could pursue a career: I wanted to write and work in media, and now I could afford to take on nonpaying internships at magazines and build my résumé.

I never told anyone in my daytime life about my “other” job — they would have reacted poorly. “Oh, honey,” one editor told me, “You don’t have to wear heels to photo shoots. Your feet are going to be dying at the end of the day.” I shrugged. I was used to being on my feet in heels much higher than the wedges I was wearing. You have no idea, I wanted to tell her.

At one point, I went to work at strip clubs in different cities, on a sort of working vacation: San Francisco, Portland, Ore. But it dawned on me that I wasn’t having new experiences as much as I was cataloging a travelogue of despair. New York, the West Coast: It was all the same — dressing rooms full of women struggling for dwindling pools of cash, indistinguishable days and nights punctuated by various iterations of ennui and despair. We performed the same tasks every night, naked, and nobody seemed to care. We could go across the country and do more or less the same job in various strip clubs or peep shows, but it wasn’t freedom. Nobody here was winning.

It was affecting my personal life, as well. I didn’t feel like I could date, working in places like that. When I did go on casual dates, I was honest about what I did. The nice guys were scared off, and the guys who didn’t have a problem with it were predictably sleazy.

Eighteen months of living a double life went by. The week before Christmas, I was working alone at 3 a.m. in Times Square. The store was completely empty, “Your Cheatin’ Heart” playing on the radio.

There was a rustle in the plastic chains separating the peep-show room from the rest of the store. I looked up: An Eighth Avenue street hustler was leading a toothless, drunken geezer into the peep-show area. The hustler pointed at me and whispered to the oldster, then collected money from the man and peaced out.

Now, the duped drunk was lurching over to me, reeking of booze, his gray hair sticking up wildly.

“I already paid $100 for a BJ,” he growled, a Southern twang seeping through his alcohol-slurred voice, “and I’m not gonna leave until I get one!” I calmly called for security. My indifference infuriated him even more, and he pounded on the wall in frustration. Two porters appeared and grabbed him by each elbow, hauling him backward out the door. After they’d taken care of him, Basil, one of the porters, came back and grabbed a mop so he could go clean out one of the video booths. We exchanged glances, acknowledging the absurdity of it all.

“You know,” Basil said, wringing the mop out into a bucket of filthy water, “there’s gotta be a better way to make a living.”

He was right. I couldn’t allow myself to be viewed and picked over like a piece of merchandise anymore. I had thought I could stay on my side of the booth, aloof and unaffected by the work. I couldn’t. No one could.

At the end of 2007, I left by simply disappearing. That was how you did it. Live girls quit by abandoning their things. The point was to not own wigs, stripper shoes and sparkly dresses anymore.

It helped that, by then, I had steady freelance work as a blogger at a Web site, and knew I could make it from there. I soon got hired full-time and began my career in earnest.

Looking back, I don’t feel guilty about what I did. It was a reactionary move, but my parents had always joked that I’d insisted on learning things the hard way every time. They weren’t wrong — I learned a lot.

Things like sex — or rather, the idea of sex — and even nakedness, are supposed to be imbued with meaning. But isolated from a relationship, they mean nothing — or rather, I realize now, they become something to be negotiated, and as a peep-show girl, I became nothing — little more than a dress-up doll for men to project their narratives onto.

Make no mistake: I am not against the stripping industry. I support any women who work there. But it’s a tough job for anyone who does it.

After I quit the peeps, I fell in love with a guy, Matt, who hated the fact that I’d worked there. “You had to work in a cage,” he kept saying in disbelief, over and over. But he had a past of his own; he’d struggled with drugs for years, and he knew what it was like to live a double life. He saw his story in mine, and he understood.

The only person I kept in touch with from the peep shows was my friend Ruby. She reported back for the first few months after I left that men were still coming into the peep show asking for me. Such requests became fewer and further between, until they stopped — and the guys, the ones who’d paid my rent over and over, forgot that a pale brunette named Chelsea had ever been there at all.

— Excerpted from “The Last of the Live Nude Girls,” out Aug. 9 from Soft Skull Press.