Proving Ground

The Untold Story of the Six Women Who Programmed the World's First Modern Computer


By Kathy Kleiman

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Discover a fascinating look into the lives of six historic trailblazers in this World War II-era story of the American women who programmed the world's first modern computer.

After the end of World War II, the race for technological supremacy sped on. Top-secret research into ballistics and computing, begun during the war to aid those on the front lines, continued across the United States as engineers and programmers rushed to complete their confidential assignments. Among them were six pioneering women, tasked with figuring out how to program the world's first general-purpose, programmable, all-electronic computer—better known as the ENIAC—even though there were no instruction codes or programming languages in existence. While most students of computer history are aware of this innovative machine, the great contributions of the women who programmed it were never told—until now. 

Over the course of a decade, Kathy Kleiman met with four of the original six ENIAC Programmers and recorded extensive interviews with the women about their work. Proving Ground restores these women to their rightful place as technological revolutionaries. As the tech world continues to struggle with gender imbalance and its far-reaching consequences, the story of the ENIAC Programmers' groundbreaking work is more urgently necessary than ever before, and Proving Ground is the celebration they deserve.


Cast of Characters

Electronic Numerical Integrator and Computer Programmers (the ENIAC 6)

Kathleen McNulty/“Kay”—Math graduate of all-women’s Chestnut Hill College in Philadelphia. She was recruited to the Army’s Philadelphia Computing Section at the Moore School in 1942 and became supervisor of a team operating the differential analyzer from 1942 to 1945. In 1945, she was chosen to program ENIAC, and moved with ENIAC to Aberdeen Proving Ground (APG) after World War II to continue her programming work.

Frances Bilas/“Fran”—Math graduate of Chestnut Hill College and Kay’s best friend. She was recruited to the Army’s Philadelphia Computing Section at the Moore School in 1942 and became the supervisor of a team operating the differential analyzer from 1942 to 1945. In 1945, she was chosen to program ENIAC, and moved with ENIAC to APG after WWII to continue her programming work.

Frances Elizabeth Snyder/“Betty”—Graduate of University of Pennsylvania. She joined the Army’s Philadelphia Computing Section at the Moore School in 1942. In 1945, she was chosen to program ENIAC, and moved with ENIAC after WWII to APG to continue her programming work. She became an early employee of Eckert-Mauchly Computer Corporation working with the first commercial computers and went on to a forty-year career at the cutting-edge of computing and programming.

Marlyn Wescoff—Graduate of Temple University. She joined an Army radar project at the Moore School in 1942 and became part of the Army’s Philadelphia Computing Section in 1943. In 1945, she was chosen to program ENIAC’s ballistics trajectory program.

Ruth Lichterman—Undergraduate studying math at Hunter College in New York City when she was recruited to the Army’s Philadelphia Computing Section at the Moore School in 1943. In 1945, she was chosen to program ENIAC and moved with ENIAC after WWII to APG to continue her programming work. She then returned to the Moore School to work on other projects.

Jean Jennings—Math graduate of Northwest Missouri State Teachers College in Maryville, Missouri. She moved to Philadelphia in 1945 to join the Army’s Philadelphia Computing Section. In 1945, she was chosen to program ENIAC. After WWII when ENIAC moved to APG, she continued her work with ENIAC, helping to design and program its Converter Code and hiring and leading a programming team to deliver the Ballistic Research Laboratory’s (BRL) first wind tunnel programs for ENIAC. She continued at Eckert-Mauchly Computer Corporation and had an active career in computing and computer publishing.

Moore School of Electrical Engineering, University of Pennsylvania

Dr. Harold Pender—First dean of Moore School. He contracted with the BRL for Moore School to host the Army’s Philadelphia Computing Section during WWII. Under his tenure, J. Presper Eckert and Dr. John Mauchly built ENIAC.

Dr. John Grist Brainerd/“Grist”—Moore School instructor, dean, and Director of Research. He was the liaison to BRL at APG for the Army’s Philadelphia Computing Section and later the ENIAC project. He was close to Lieutenant Herman Goldstine.

Joe Chapline—Beginning in May 1942, he was a research associate at Moore School and a maintenance engineer on the differential analyzer. He was a champion of John’s computing ideas and connected Herman Goldstine with John Mauchly.

Dr. John Mauchly—Received his PhD in physics from Johns Hopkins University. He was a professor at Ursinus College when he left to answer the Army’s call for men with electronics abilities during World War II. He was cofounder of Eckert-Mauchly Computer Corporation and co-inventor of the world’s first general-purpose, programmable, all-electronic computer, ENIAC, and its successors BINAC (Binary Automatic Computer) and UNIVAC (Universal Automatic Computer), the first modern commercial computers.

J. Presper Eckert Jr./“Pres”—Electrical engineering graduate of the Moore School. He was a lab instructor there when Mauchly first met him. He was cofounder of Eckert-Mauchly Computer Corporation and co-inventor of ENIAC, BINAC, and UNIVAC and was considered one of the finest electrical engineers of the twentieth century.

Dr. Irven Travis—Electrical engineering professor at the Moore School who was called to active duty in 1941. He returned in 1946 and became Director of Research. He ended up clashing with John and Pres over patent rights.

Ballistic Research Laboratory, Aberdeen Proving Ground, Aberdeen, Maryland

Colonel (later Major General) Leslie E. Simon—Director of BRL during WWII. He created the Army’s Philadelphia Computing Section at the Moore School during WWII with Captain Paul Gillon and worked with John Grist Brainerd and Herman Goldstine. He negotiated and approved the contract with the Moore School to build ENIAC and relocate it to BRL after its acceptance by the Army.

Captain (later Colonel) Paul N. Gillon—Assistant Director of BRL during WWII. He was Herman Goldstine’s senior officer and cocreator of the Army’s Philadelphia Computing Section at the Moore School with Colonel Simon. He supported BRL’s funding of ENIAC and worked with the Moore School team from time to time.

Lieutenant (later Captain) Herman Goldstine—PhD in math from University of Chicago, where he studied under Dr. Gilbert Bliss. After being sent to BRL during WWII, he was assigned to head the Army’s Philadelphia Computing Section at the Moore School and served as liaison from BRL to the Moore School. He introduced the BRL to the idea of ENIAC and was involved in its construction and demonstration. After WWII, he was a member of Princeton’s Institute for Advanced Study (IAS) and then went to IBM.

Adele Goldstine (née Katz)—Graduate of Hunter College, with a master’s degree in math from University of Michigan. She revamped instruction at the Army’s Philadelphia Computing Section at the Moore School to educate dozens of young women in graduate-level numerical analysis for trajectory calculations. She wrote the technical manual for ENIAC and after WWII helped design the ENIAC Converter Code and helped convert ENIAC to one of the world’s first stored-program computers. She was the wife of Herman Goldstine.

John Holberton—Beloved civilian supervisor of the Army’s Philadelphia Computing Section, he reported to Lieutenant Goldstine and worked with him on the ENIAC project too. He moved with the ENIAC to APG after WWII and spent a career in computing.

Major General Oswald Veblen—Professor at Princeton for decades and early member of the Institute for Advanced Study. He joined APG during WWI and worked on ballistics research and calculations. He founded a program to calculate ballistics trajectories for APG, which he insisted continue between WWI and WWII. He was named Chief Scientist of BRL during WWII and made the final decision to fund ENIAC.


As I stared at the women in the black-and-white photograph, it seemed as though they were trying to tell me something. I was sitting in Harvard’s Lamont Library, a main library for undergraduates, trying to research a paper on American women in the twentieth century who were leaders in computing. I knew of only one, Captain Grace Hopper of the US Navy, later Rear Admiral Hopper. Of course, there was Lady Ada Lovelace, daughter of British poet Lord Byron, who worked on early programming concepts in the nineteenth century, but she was out of scope for an American women’s history course.

I was a young woman in computing, and I wanted to know if there were others. I had taken computer science since I started college, and while my early programming courses were composed of about half women, my latest class had only one or two. I knew I would feel more comfortable in computing if I saw a few more women in class with me, and this drove my interest in who came before me and what they had done.

Open before me, spread across the reading room table, were encyclopedias of computer science and histories of computing. Noticeably absent in all of them were the names of women, except Ada and Grace. But noticeably absent, too, was any real history of programming. The stories were all about hardware and the men who built the mainframe computers that dominated computer history in the 1940s, ’50s, and ’60s.

But what about those who pioneered ways to communicate with the large computers? Instruction codes and programming languages also date back to the 1940s, ’50s, and ’60s, but where were the stories of the people who wrote them?

Then I stumbled on a black-and-white photograph of a huge, black, metal computer dominating three sides of a large room and dwarfing six people—four men and two women.

University Archives and Records Center, University of Pennsylvania

There were two men in the middle of the photo, two women on the right with a man in uniform between them, and a man in the back left. Only the two men in the middle were named—J. Presper Eckert and Dr. John Mauchly, co-inventors of ENIAC, the world’s first all-electronic, programmable, general-purpose computer. It was built at the University of Pennsylvania (Penn) during World War II. Nowhere in the captions or accompanying article were the other people in the photograph named.

I studied the image closely, especially the women. They were young, with World War II–era hairdos, flat shoes, and skirt suits. As I leaned in closer, what struck me was that they seemed to know something about ENIAC. They appeared to be comfortable, knowledgeable as they adjusted knobs on and read documents next to this vast, seemingly living and breathing giant. I could not stop looking at them.

I knew something about computers. My father was an electrical engineer who specialized in new technologies. He brought home electronics for us, including an early calculator, clunky and huge compared to today’s versions, with only a few functions, but fascinating and fun to play with. He was the first person I knew to talk about speech synthesis and voice recognition. My father had written his dissertation on the founding of the semiconductor industry and was certain that the miniaturization of electronics would continue and would keep changing the world.

Friends asked me in junior high school if I wanted to learn to program computers, and I said yes. So I joined an Explorer Post, a coed branch of the Boy Scouts dedicated to career exploration, and went off to spend my Wednesday nights at Western Electric, a manufacturing arm of AT&T near my home in Columbus, Ohio. I learned BASIC, a programming language invented at Dartmouth in the 1960s. Soon I was playing games my friends wrote and adding one of my own, a version of Mad Libs that I wrote in BASIC. The first time my friends played it and laughed out loud at the funny story the computer printed, I knew I was hooked on programming.

Looking at the old black-and-white picture, and the men and women standing before ENIAC, I longed to know more about their story. I dug deeper, found more books, and uncovered another photograph. This one was a close-up showing two young women standing right in front of ENIAC. Once again, no names of the women, only the name of the computer.

University Archives and Records Center, University of Pennsylvania

I made copies of both pictures and took them to my professor. Anthony Oettinger was a former president of the Association for Computing Machinery, an international group for computing professionals.

I showed him the two ENIAC photographs. “Who are the women?” I asked.

“I don’t know,” Professor Oettinger answered, “but I know who might.”

He told me to visit Dr. Gwen Bell, cofounder of the Computer Museum, then in Boston and now in Silicon Valley.

The Computer Museum was at the far end of Museum Wharf in downtown Boston. As I walked down the long wharf, I noticed the Children’s Museum and in the water, the Boston Tea Party ships. All great to visit, but I was on a different mission as I clutched my folder of photographs and disappeared into the Computer Museum.

I found my way to the office of the museum’s director. Bell was in her early fifties with short, dark, graying hair, clearly a no-nonsense, busy person. I opened my folder and once again found myself pointing to the black-and-white images of the women who were standing in front of ENIAC.

“Who are the women?” I asked Bell.

Unlike Professor Oettinger, she knew. “They’re refrigerator ladies,” she said.

“What’s a refrigerator lady?” I asked, baffled as to what she was talking about.

“They’re models,” she responded, rolling her eyes. Like the Frigidaire models of the 1950s, who opened the doors of the new refrigerators with a flourish in black-and-white TV commercials, these women were just posed in front of ENIAC to make it look good. At least that’s what Dr. Bell thought.

She closed my folder and handed it back to me. I was dismissed.

I slowly headed out of the museum. I saw the children lined up on the wharf getting ready to enter the Children’s Museum, the Boston Tea Party ships rocking in the harbor, and the bright blue sky. But Bell’s story did not make sense to me. I had stood in front of big computers before. The first time you see them, they seem huge, overwhelming, almost surreal. The young women in the ENIAC pictures looked confident and assured. They looked like they knew exactly what this huge computer did and why they were in the photos. They did appear posed, but so did the men, and the men were not models.

As I left the wharf, I set a task for myself. I was going to find out the names of the women. I would learn what they had done in order to be in these beautiful, black-and-white pictures of ENIAC in the 1940s.

I was going to learn their story.

The Double Doors Open

The women walked down the stairs from the second floor, their saddle shoes squishing against the marble. All of the students and professors at the Moore School of Electrical Engineering were men, and the women were used to being hazed, ogled, and mocked when they walked down the hallways or down to the differential analyzer room, where some of them had worked.

But this time the hallways were quiet. Betty, Jean, Kay, Fran, Marlyn, and Ruth—the six women assigned to program solutions for Army ballistics trajectory problems—all twentysomethings, turned right and stopped at a set of double doors. A sign read RESTRICTED. For three and a half months, in classrooms, an antechamber, and a repurposed nearby fraternity house, they had been familiarizing themselves with the computer behind the door, studying diagrams and piecing together the puzzle of how to use it. But they had never once been granted the privilege of seeing the computer that they would program. They had been prohibited from setting eyes on it—until now.

It was mid-November 1945, almost three months after the official surrender of the Japanese, and the women’s boss, Captain Herman Goldstine, serious-minded with an officious air, was walking in front of them. With no warning, he had summoned them down from the second-floor classroom in which they had been working.

The double doors swung open, and they came face-to-face with the Electronic Numerical Integrator and Computer—the great ENIAC, all forty-five units of it. They had nearly given up asking when they would see it, let alone move the switches and wires and cables they had come to know so intimately on paper over the past three months. But now everything had changed, and they came out of the classroom and followed Herman down the wide concrete steps to the first floor.

It was like meeting someone in person for the first time, after studying their face in photographs. A series of black steel units, each eight feet tall and two feet wide, stared down at them. The units stood in the shape of a huge U—sixteen on the left side, eight at the base, sixteen more on the right. Three square units on wheels stood at odd places around the room, while the remaining two units, an IBM card reader and an IBM card punch, were connected by wires. The women were delighted.

Curious to get a better look, they walked around the large thirtyby-sixty-foot room. The units had been pushed away from the wall so that the engineers could work on the backs. The women took in ENIAC’s depth, a few feet. They inspected the great U and examined the units and their switches. They were impressed: They knew this huge computer was capable of completing 5,000 additions in a second and 500 multiplications in the same second, not to mention lightning-fast divisions and square roots.

Even with the AC roaring, they could feel the heat coming off the tubes and hear their low hum. It had taken more than 200,000 hours of work to build ENIAC and cost just under $500,000—equivalent to just over $7 million today. The women had closely studied the machine on paper, but to see it before them in real life was surreal. They walked around the room completely absorbed by ENIAC, oblivious to the other people in the room.

Too soon, their senior supervisor Herman Goldstine brought them out of their reverie with his command: “We’re going to put a problem on.” They looked up and realized there were about a dozen people already inside the room that they had missed while gazing around in wonderment. These included some young ENIAC engineers (builders of the computer) and Herman’s wife, Adele, a mathematician who had trained some of the women to calculate ballistics trajectories when they first started their Army work. There were also two men from an Army base in New Mexico who the women had met briefly that summer, Dr. Stanley Frankel and Dr. Nicholas Metropolis.

Herman quickly assigned the women to work with various other people in the room, and they took their places around the units of ENIAC. Metropolis and Frankel distributed small, prepared slips of paper that were slid into metal slots at the front of many of the units.

Engineers had been testing small problems on ENIAC, such as tables of squares and cubes, but this new problem, which no one explained, seemed to take up almost the whole machine. As everyone awaited the next command, there was a moment of silence.

Standing in the center of the room, Herman lifted his hands like an orchestra conductor. It would direct the actions of the entire group as they strung wires across the computer and hoisted 50-pound digit trays into place.

The young women were about to do something they had never done before, but they had a shared history that made them exuberant and optimistic. They would work on ENIAC the same way they had done everything since they began their collective journey more than three years earlier: by sitting at desks typing numbers into clunky calculators; by holding what they liked to call “bull sessions” in their barracks; by squinting at enormous diagrams to learn ENIAC’s units in borrowed rooms on the Penn campus. They would teach themselves to program a computer they were not even allowed to see.

And they would do it together.

Looking for Women Math Majors

On a cloudy day on Tuesday, June 2, 1942, Kathleen “Kay” McNulty, twenty-one years old, smiled and took her bachelor’s in mathematics diploma from Reverend Hugh L. Lamb, Auxiliary Bishop of the Archdiocese of Philadelphia.1 She had dancing eyes, a narrow face, and dimples. It was commencement at Chestnut Hill College, a Catholic women’s school in the northwestern edge of Philadelphia, overlooking the Wissahickon Creek. Kay was one of 107 graduates.2

The commencement was outside, near the tennis courts, and the principal address was also delivered by Bishop James Kearney of Rochester. One of Kay’s best friends, Frances “Fran” Bilas (pronounced BEE-las) received many awards that day, including one from the National Catholic School Press Association, the Student Teacher’s Gold Key Award, and a Kappa Gamma Pi certificate “for graduation with distinction and leadership in extra-curricular activities.”3 Kay knew Fran was one of the smartest students in the class. As Kay and Fran met their families, clutching their degrees in their hands, both of them knew that they were starting the next chapters of their lives.

It was a strange time to be a young American entering the job market. At the University of Pennsylvania commencement exercises, which took place the same day, seventy-three degrees were awarded in absentia to young men who had already joined the armed services. The Philadelphia Inquirer might have been addressing Fran and Kay with the headline it ran above photos of different area commencements: STUDENTS GRADUATING INTO WORLD AT WAR.4

The Women’s Undergraduate Record, the yearbook for women at the University of Pennsylvania for 1941, declared that the war was

a great sorrow to the world… Even though we were not actively engaged in it, it is a war world in which we live. We cannot isolate our sympathies, even though we may hope to isolate our nation. Our eyes are on Europe and her guns strike our hearts. The maturity of Seniority has been accepted by the sober thoughts that are with us all.5

Kay and Fran had been two of only three math majors in their class at Chestnut Hill College; the third, Josephine Benson, was also their best friend. Kay had picked math because it was easy and fun for her. A few days into college, an adviser asked her to pick a major, telling her to choose the subject she liked best. “Mathematics,” she immediately responded. For her, math was “no work. It was a no brain thing for me. It was just like a wonderful puzzle that you could do and there was always an answer.”6

Most women who entered Chestnut Hill College during the Depression majored in home economics, the study of life skills such as cooking, sewing, and finance. In fact, just a few weeks before Kay, Fran, and Josephine’s commencement, Chestnut Hill’s home economics department presented a fashion show in the school auditorium. A hundred gowns were modeled by students, with a patriotic theme, due to the war.7 Many young women in Kay’s class wanted to be dietitians in schools or hospitals. Then they would marry and have children. Home economics could help them in the dietitian field, but that wasn’t the point; they had to learn how to cook and run a household well if they were going to be good housewives.

Kay was not like many of the other students. She wanted to do something important, and eventually she wanted to start a family. And she did not think the two were mutually exclusive.

Not two weeks after she graduated, she spotted a notice in Philadelphia’s Evening Bulletin: LOOKING FOR WOMEN MATH MAJORS. The Army sought women to work at the University of Pennsylvania’s Moore School of Electrical Engineering. She didn’t know what the job was but thought it amazing that a job for women with degrees in mathematics “would be advertised in the paper.”8 Before the war, this would have been unheard of; ads for math-related positions (such as accountants and actuaries) were in the “Male Help Wanted” section of the newspaper. Math was a man’s job. In the “Female Help Wanted” sections, there were jobs for secretaries, nutritionists, nannies, and laundresses.9 Those interested in the Moore School opportunity were to report to a recruiting office on South Broad Street in South Philadelphia, inside the Union League, a storied private club that also contained offices.10 Kay called Fran and Josephine and said they should all interview together.

But Josephine already had a job. And so the next day, Kay showed up with only one best friend, not two.

All over the country, American women were seeing notices telling them they were needed for war work. Many of these ads were for industrial positions. With brothers, cousins, uncles, and fathers volunteering for service and being drafted, the government and military began a deliberate strategy to recruit women into factories and farms, for now-vacant positions.

During the Great Depression, it had been difficult for both men and women to obtain jobs. Unemployment soared to 24.9 percent in 1933 and remained above 14 percent from 1931 to 1940.11 During World War II, the government encouraged women to fill the jobs formerly open only to men—and women enthusiastically responded. From 1940 to 1945, the percentage of women in the workforce increased by 50 percent.12

If the country were to clothe, feed, and provide guns, artillery, planes, and tanks to the armed forces, its women would have to take jobs in industrial manufacturing and in labor. The fictitious Rosie the Riveter, later the subject of a WE CAN DO IT!


  • "Kleiman’s persistence in sleuthing out the story of the ENIAC 6 programmers has resulted in an admirable contribution to the historical record and a labor of love."—Wall Street Journal
  • “While early women programming pioneers Ada Lovelace and Grace Hopper have taken their place in the annals of computer history, Kleiman shows us that there were other women programmers — like the ENIAC 6 — who deserve to be recognized as well.”—Associated Press
  • "[Author] Kleiman became obsessed with learning the identities of all the earliest women programers. The result of that magnificent obsession was a documentary in 2014 and this book, which melds social history with the major events of the second world war and the biographies of these six remarkable pioneers to produce an irresistible narrative."

     —The Guardian
  • “Everyone told Kathy Kleiman that the women she sought did not exist. Thankfully, she didn’t believe them. In Proving Ground, Kleiman pursues her subjects with the instincts of an investigative journalist, uncovering the stories of six groundbreaking women who battled sexism, complex trajectory equations, and blown vacuum tubes in order to program the world’s first digital computer. With unforgettable, detailed prose, Kleiman blends the history of early computing with the lives of the women who made modern programming possible. Proving Ground is a book so deeply inspiring that it has the power to completely alter how we see the technology field and the role of women within it.”—Nathalia Holt, New York Times bestselling author of Rise of the Rocket Girls
  • “With this book, Kathy Kleiman restores the ENIAC 6 to their rightful, lauded place in the history of computing. The bond she developed with these women through her years of research and interviews is evident, as each of them come vibrantly and vividly alive in her writing. Their story will serve as inspiration for generations of women in STEM.”—Keith O’Brien, author of Fly Girls
  • “Kleiman has a novelist’s gift for crafting a page-turning narrative, and the one on offer is both revelatory and inspiring. Fans of Dava Sobel’s The Glass Universe and Margot Lee Shetterly’s Hidden Figures are in for a treat.”—Publishers Weekly, starred review
  • “Kathy Kleiman's courageous pursuit across decades discovering and sharing the story of the extraordinary contribution of these first programmers and founding inventors gives us a gift that can change the future - empowering a more welcoming technical innovation culture for all.”—Megan Smith, Former United States Chief Technology Officer and CEO shift7
  • "An important and inspiring little-known narrative in modern computing history."—Kirkus Reviews
  • "Kleiman excels at capturing the pressures of working in technology during a highly stressful period in history, particularly when the results of technological trials directly impacted war efforts. . . [T]he inclusion of direct interviews with the women and the clear passion for their stories make Proving Ground a needed and welcome addition to the shelves of computer history."—Booklist
  • "A compelling account of a group of pioneering women."

    Library Journal
  • "Kleiman explores the lives of [the ENIAC six] and their ground-breaking work in this inspiring history. "—Arlington Magazine
  • "Kathy Kleiman’s debut nonfiction is a celebratory biography of the six women who helped program ENIAC, the first general-purpose computer. In engaging prose, she describes how the women found opportunities during World War II, while many men were overseas, and overcame discrimination and harassment to accomplish their important work."—Christian Science Monitor

On Sale
Jul 25, 2023
Page Count
320 pages

Kathy Kleiman

About the Author

Kathy Kleiman is a leader in Internet law and policy and currently teaches at American University Washington College of Law. Her passion for finding the truth behind these female programmers led to her founding the ENIAC Programmers Project, which completed a documentary on the subject of this book titled "The Computers: The Remarkable Story of the ENIAC Programmers." The film premiered at the Seattle International Film Festival in 2014 and won the UNAFF Grand Jury Award For Best Short Documentary at the United Nations Association Film Festival in 2016.  

Learn more about this author