Jonathan Eig searches for the characters of his new book

In previous books, best-selling author Jonathan Eig profiled baseball legend Lou Gehrig and Chicago gangster Al Capone. But as he set about researching his most recent project, he faced an interesting dilemma: what do you do when your main character is a little round pill? In this installment of the Storyboard feature "Writing the Book," Eig, a former Wall Street Journal reporter, discusses the challenges of finding and establishing the protagonists of his new book, "The Birth of the Pill." You can read the New York Times review of the book here.

Before I could begin writing my latest book, I had to kill Allan Pinkerton.

I was fascinated with Allan Pinkerton. I still am, really. But that didn’t stop me. The more I researched the life of the legendary detective, the more I grew to dislike him and the more I came to believe that he would never be good to me or anyone else. So I killed him. I buried him in the basement next to some of my other recent victims and set out looking for someone or something else to write about.

“Write a book women will want to read,” my wife said.

“Are you saying that women don’t care about my other books?” I asked.

When I stopped feeling defensive, I started making lists, as I always do when I’m searching for ideas. There are so many things I’m interested in writing about that making lists is easy. The hard part is narrowing down. I look for stories with conflict and passionate characters, because conflict and characters move plot. I look for stories that might give me something important to say, because Melville said to write a mighty book you must choose a mighty theme. I look for stories that might attract big audiences, because I like for my work to be read and I like getting paid.

This time, I also looked for a story that women might want to read, because I love my wife and she’s always right.

Here are some of the lists I made: most important Supreme Court cases; most important inventions; most important Jews; most important women; most important athletes; most important women athletes.

After a couple months of building lists, I noticed that the birth-control pill had popped up several times. It made my list of important inventions; in fact, The Economist had called it the most important invention of the twentieth century. Margaret Sanger, the crusading feminist who coined the term birth control, made my list of important women. And Gregory Pincus, the scientist who invented the pill, made my list of important Jews. Now I had a Venn diagram in my head with three overlapping circles.

It struck me as odd that I knew so little about the origin of the pill. The more I thought about it, the odder it seemed. Why would anyone invent a birth-control pill in the first place? To give women more power? That seemed unlikely. To help women better enjoy sex? Even more unlikely. In the 1950s, before the pill, men had almost complete control of government, science and business. What motivated the men in charge of these institutions go to work on a new contraceptive? And if men in charge didn’t make it happen, who did?

I knew something about Sanger and her longtime cause, which dated back at least to 1914. It was Pincus who intrigued me. Who was he and why had I never heard of him? What was in it for him? Every other scientist Sanger had approached told her no, they would never agree to work on a birth-control pill; it was too controversial, they said, and ultimately pointless. No company would ever manufacture such a pill and the FDA would never approve it.

I called Pincus’s daughter, who lived in Boston, and arranged to meet her. When she told me her father’s story, I was hooked. Pincus had been dismissed by Harvard in the prime of his career because he’d been too radical. He’d been working on in vitro fertilization in the 1930s and bragging to reporters that his work would change forever the way men and women reproduced. The world wasn’t ready. When Harvard denied him tenure, Pincus couldn't find work anywhere, so he built his own laboratory and started his own foundation in the garage of an old house in Shrewsbury, Mass. Twenty years later, he agreed to take on Sanger’s birth-control project in large part because he had nothing to lose.

Let’s look back at my checklist for good stories.

Conflict? Check.

Passionate characters? Check.

Important? Check.

Ability to attract a big audience? Who the hell knows?

Something for women? Check.

The first two “checks” excited me most. This story had a ton of conflict and a great cast of characters. Sanger and Pincus were classic heroes--outsiders summoned to perform a seemingly impossible mission. And they were acting not for fame or glory. They fought to give women equality, make sex more fun, and prevent the planet from becoming overpopulated. Sanger, who was in her seventies and suffering from heart failure, sincerely believed that Pincus might get this done while she was still around to see it.

From a storytelling perspective, there was one big challenge. In addition to Sanger and Pincus, I had two more compelling characters: Katharine Dexter McCormick, the heiress who financed the entire research project; and Dr. John Rock, the Catholic gynecologist who defied the church to lead the clinical trials. Constructing a narrative around four characters is tricky. Was the pill the hero of my story, or was it this team of crusaders?

For inspiration, I went back and re-read Laura Hillenbrand’s “Seabiscuit,” which is one of my favorite recent works of non-fiction. There are chapters in that book that could be books on their own—it’s so rich. Seabiscuit made for a problematic central character because horses, with the exception of Mr. Ed, don’t talk. Hillenbrand overcame the problem by making heroes of three men surrounding the racehorse—the owner, trainer, and jockey.

It’s a nifty trick on her part. Hillenbrand describes Seabiscuit as an unlikely champion, with an awkward stride and a sad little tail. Even so, the reader never really cares about the horse. We know, win or lose, that Seabiscuit is going to get a warm paddock and plenty of oats. The humans are the real heroes. We care about Seabiscuit because they do.

In their quest for a birth-control pill, Sanger, Pincus, McCormick and Rock were fighting long odds. It was illegal to disseminate birth-control products or even information about birth control in most of the United States in 1950, when they began their work. The Catholic Church would fight them all the way. If those obstacles weren’t enough, consider this: the birth-control pill would be the first medicine designed for daily use by healthy people. If it made women sick or led to deaths, the results would be catastrophic.

Yet Pincus, Sanger, McCormick and Rock pushed ahead because they were true believers. In their minds, even the greatest risks were acceptable because the potential rewards were so enormous. And it was here, as these men and women took risks, that I was able to add the most new detail to the story of the pill’s invention. Patients had no privacy in the 1950s. Women participating in scientific experiments were not asked to give their consent.

At the Library of Congress, among Pincus’s papers, I found letters he wrote to gynecologists asking them to engage in what Pincus no doubt considered a minor and harmless deception. He asked the doctors to give birth-control hormones to women seeking treatment for infertility. The women would be told that these hormones would rest their reproductive systems. When they finished treatment, their systems would kick back into gear and they might be more fertile. In truth, Pincus was interested in only one thing: making sure his hormones shut down ovulation.

Then he tried testing the birth-control formula on mental patients at the Worcester State Hospital. He tried it on men as well as women there. I found lists of names. I tracked down some of the children of the women who were tested. They told me their mothers had no idea. Doctors at the hospital confirmed it. They said they injected men and women with all kinds of experimental drugs, never asking for their permission and seldom offering explanations.

After testing their birth-control formula in the insane asylum, Pincus and Rock traveled to the slums of San Juan, Puerto Rico, and conducted large-scale field trials on women there, where American laws would not apply. They gave women massive doses because they knew the Food and Drug Administration would assess the drug only based on its effectiveness, not on its side effects. They weren’t too considered with women suffering nausea and headaches just so long as the pill came close to 100 percent effectiveness.

Pincus and Rock were operating well within the ethical standards of their time. In fact, they considered themselves progressive—both in their treatment of women and in their scientific methods. In the 1950s, they really were more sensitive and more concerned with women’s rights than most men. This is what made them such compelling heroes—they weren’t perfect, and they were willing to take chances for something they strongly believed.

“Seabiscuit” and my book had one more thing in common: predictable endings. Before they turn a single page, readers of both books will know the horse is going to win the big race, just as they know the pill will win approval and change women’s lives.

But with strong characters and plenty of conflict, predictable endings are not necessarily bad. My book hinges on the FDA decision to approve the birth-control pill, which went by the brand name Enovid. In writing those critical pages, I pretended that I didn’t know the outcome of the agency’s decision. It wasn’t hard. I spent three years working on this book, and speaking to dozens of men and women who had known these characters. Every time I met with Pincus’s daughter or Rock’s daughter, I felt like I was looking into my characters’ eyes, that I was getting at least a glimpse at how they might have moved, how they might have spoken, how they might have felt. A writer can't really know what’s in his subject’s heart, but he can try. At the very least, the writer can try to see the story through his character’s eyes. And so I tried to remember as I wrote the book’s climax that my characters didn’t know how it would end. I came to love these characters, and I was rooting hard for them to see their hard work pay off.

If I did my job, readers will feel the same way.

They’ll be rooting for the pill as it comes down the stretch.

As for me, I’ll soon be moving on to another book. Pincus, Rock, McCormick, and Sanger will be carried from my office to the basement. But they won’t be buried alongside Pinkerton. Pinkerton got a cardboard box. These heroes will get a fireproof file cabinet.

They earned it.

Jonathan Eig is the New York Times best-selling author of four books: "Luckiest Man," "Opening Day" "Get Capone" and, most recently, "The Birth of the Pill." He is currently working on a biography of Muhammad Ali. Before writing books, Jonathan worked as a reporter for The Wall Street Journal, Chicago magazine, The Dallas Morning News, and the New Orleans Times-Picayune. His work has also appeared in The New York Times, Esquire and The Washington Post.