National History Day 2027 · Innovation in History
The Invisible Six
The Women Who Programmed ENIAC and Were Written Out of History
Hover or tap to bring their names back.
In 1945, the U.S. Army finished ENIAC, a thirty-ton electronic computer meant to help win World War II. The war ended before it was ready. Its most lasting innovation was programming, worked out by six young women hired to do math by hand. When ENIAC was introduced to the world, their names were left out, and they stayed invisible for about forty years.
Chapter 1 of 7
When Computers Were Women
Before it was a machine, a computer was a person.
Before ENIAC, the word "computer" described a person. During World War II, the Army's Ballistic Research Laboratory hired women with mathematics degrees to work as computers at the University of Pennsylvania's Moore School of Electrical Engineering in Philadelphia.
With so many men overseas, these jobs gave women a rare chance to use their education. Each computer spent long days solving trajectory equations on a desk calculator, so soldiers would know how to aim. Some of these women would soon run the machine that was built to replace them.
- A person who makes calculations, especially one employed to do so.
- An electronic machine that processes data.
"This announcement came around that they were looking for operators of a new machine they were building called the ENIAC.... Of course, I had no idea what it was, but I knew it wasn't doing hand calculation."
Quoted in Laura Sydell, "The Forgotten Female Programmers Who Created Modern Tech," NPR, October 6, 2014. Find the original in her Computer History Museum oral history (2008).
Chapter 2 of 7
20 Hours for One Shot
The weapons were ready. The math was not.
Artillery crews aimed with firing tables, printed charts that told them how high to raise a gun's barrel to hit a target at a given distance. Each new gun and shell needed its own table, built from thousands of calculations.
A skilled human computer needed about twenty hours for one sixty-second trajectory. The Army's best mechanical calculator, the differential analyzer, took about fifteen minutes. In 1942, physicist John Mauchly proposed a far faster calculator built from vacuum tubes, and in June 1943 the Army agreed to fund it.
One trajectory, step by step
Trajectories finished in one 8-hour day
John W. Mauchly, "The Use of High Speed Vacuum Tube Devices for Calculating," memo, August 1942. Quote one sentence where he proposes the idea.
University of Pennsylvania Archives; reprinted in Brian Randell, ed., The Origins of Digital ComputersChapter 3 of 7
The Machine That Missed the War
It was built to win a war that ended before it was ready.
The Army code-named the secret project PX. Engineers J. Presper Eckert and John Mauchly led the team that designed ENIAC, the first general-purpose electronic digital computer. Britain's Colossus machines came earlier, but they could only break codes.
ENIAC used about 18,000 vacuum tubes instead of mechanical gears, but it had no keyboard, no screen and no memory for instructions. Every problem had to be set up by hand with cables and switches.
ENIAC was not working until late 1945, months after Germany and Japan had surrendered. Its first major assignment, on December 10, 1945, was a secret calculation for the nuclear weapons laboratory at Los Alamos.
Floor plan of the ENIAC room
"A new machine that is expected to revolutionize the mathematics of engineering and change many of our industrial design methods was announced today by the War Department.... The speed of this computer is phenomenal."
War Department, Bureau of Public Relations, press release for release February 16, 1946. Smithsonian National Museum of American History, Computer History Collection"Problem A—12/10/45"
The log entry recording ENIAC's first problem, the secret Los Alamos calculation.Cited in APS News, "December 1945: The ENIAC Computer Runs Its First, Top-Secret Program"; original in ENIAC recordsMyth check
A famous legend says ENIAC dimmed Philadelphia's lights whenever it was switched on. There is no reliable evidence for it.
Chapter 4 of 7
No Manual, No Problem
They were handed a thirty-ton machine and no instructions.
In the summer of 1945, six women were chosen from the Army's human computers to become ENIAC's first operators. No manual existed yet. At first they were not even allowed into the machine's room, so they taught themselves by studying its wiring and block diagrams.
Programming ENIAC required a new way of thinking. The women broke each problem into hundreds of small steps, decided which of the forty panels would handle each one, and worked out the exact order. Then they turned that plan into a physical pattern of cables and switches. When a result was wrong, they could trace it to a single failed vacuum tube.
Their greatest test came in February 1946. Jean Jennings and Betty Snyder prepared the trajectory calculation for ENIAC's public demonstration, and it ran successfully in front of reporters. The engineers had built a remarkable machine, but these six women figured out how to make it useful.
A program was a pattern of cables
"They gave us these great big block diagrams of the ENIAC.... We didn't see the machine because it was classified, and they didn't let us see it until our classification came through."
Jean Bartik, interview by Janet Abbate, August 3, 2001, IEEE History Center Oral History #576 (ethw.org)
A clip of one of the women describing how they programmed ENIAC, from the documentary The Computers or a recorded oral history. Note its length for the home page.
Chapter 5 of 7
Wired Out of History
They made the machine work. Then the story was told without them.
On February 15, 1946, the Army dedicated ENIAC at the University of Pennsylvania, and newspapers celebrated the "giant brain." The War Department's press release praised the machine, its engineers and the Army. It did not mention the six women who made the demonstration work.
According to Jean Jennings Bartik, the programmers were not invited to the celebration dinner afterward. Photographs of them at the machine appeared in newspapers, often without their names.
In the 1940s, building hardware was considered real invention, while setting up the machine was seen as clerical work, like typing. Because women did it, people assumed it was simple.
Front page, 1946
Electronic Computer Flashes Answers, May Speed Engineering
Photo heading: "New All-Electronic Computer and Its Inventors"
T. R. Kennedy Jr., The New York Times, February 15, 1946, p. 1. Read it in ProQuest Historical Newspapers or at computerhistory.org.
Credited in 1946
Not named
"The original idea for the electronic general purpose calculator was that of Dr. John W. Mauchly.... Mr. J. Presper Eckert, Jr., a recent graduate of the Moore School, joined with Dr. Mauchly..."
War Department press release, February 16, 1946. It names the engineers and Army officers, but not the six programmers."They all went out to dinner at the announcement.... We weren't invited and there we were."
Quoted in NPR, "The Forgotten Female Programmers Who Created Modern Tech," 2014. She tells the full story in Pioneer Programmer (2013)."The engineers thought programmers were far less than engineers!... Now the men had professional ratings, but they didn't give them to women."
Jean Bartik, interview by Janet Abbate, August 3, 2001, IEEE History Center Oral History #576 (ethw.org)Still invisible today
Even today, the National Archives describes a 1946 photograph of two of them only as "two of the six programmers," without their names.
National Archives, NAID 594262, as presented on DocsTeach.orgChapter 6 of 7
From Six Women to Every Screen
The machine was retired in 1955. Their ideas never were.
ENIAC's real impact came after the war. In 1947 it moved to Aberdeen Proving Ground in Maryland, where it worked on firing tables, weather forecasts and atomic research until 1955.
The women's influence lasted longer. In 1948, Jean Jennings Bartik led a team that converted ENIAC to run stored programs, the way modern computers work. Bartik and Betty Snyder Holberton went on to UNIVAC, the first major American commercial computer, and Holberton helped shape early programming languages, including COBOL.
In ENIAC in Action, historian Thomas Haigh and his co-authors argue that programming ENIAC was a team effort, so calling the six "the first programmers" oversimplifies it. Yet the six were central to that team, and history forgot them.
From ENIAC to today
- 1943The Army signs the ENIAC contract.
- 1945The six are chosen, and ENIAC runs its first problem.
- 1946ENIAC is unveiled without their names.
- 1948Bartik's team converts ENIAC to stored programs.
- TodaySoftware runs phones, cars and AI.
Chapter 7 of 7
"Refrigerator Ladies"
For forty years, they were mistaken for models.
In the mid-1980s, Harvard student Kathy Kleiman found old photographs of women working on ENIAC. When she asked who they were, a historian said they were probably models, or "refrigerator ladies."
Kleiman did not believe it. She tracked down the women, recorded their stories and spent decades getting them recognized. In 1997, all six entered the Women in Technology International Hall of Fame.
"People never recognized, they never acted as though we knew what we were doing. I mean, we were in a lot of pictures."
Quoted in NPR, "The Forgotten Female Programmers Who Created Modern Tech," 2014Email the ENIAC Programmers Project (eniacprogrammers.org) to request a short interview with Kathy Kleiman. Ask what she felt when she first identified the women, and use one quote or a clip of up to 30 seconds.
Conclusion
Invisible No More
ENIAC was built for a war that ended before it was ready, yet it changed the world. Its greatest innovation was programming, invented by six women who taught themselves a machine no one else understood. They were written out of history once. Knowing their names changes who we picture when we hear the word "computer."
Required written material
Process Paper
We are both interested in artificial intelligence and technology, so we wanted to understand where computers began. When we looked for a topic that fit the theme "Innovation in History," ENIAC seemed like a natural choice. Then we learned that ENIAC was programmed by six women who were left out when it was introduced to the public, and that decades later their photographs were mistaken for pictures of models. That surprised us, and we wanted to find out how it happened and why.
We began with secondary sources, including Kathy Kleiman's Proving Ground and the U.S. Army Research Laboratory's history of ENIAC, to understand the basic story. Then we searched for primary sources. The most valuable was Jean Jennings Bartik's 2001 oral history interview with the IEEE History Center, because it let one of the six describe the work in her own words. We also found the 1946 War Department press release, the New York Times front page, a 1941 Army firing table and the first ENIAC manual in the collections of the Smithsonian, the Computer History Museum, the National Archives and the Internet Archive. Our biggest surprise was learning that ENIAC was finished after World War II had already ended.
We chose a website because it allowed the women's own words and photographs to tell much of the story. We worked on the research together and divided the chapters between us to write. The 1,200-word limit forced us to cut a great deal. One hard choice was leaving out details we found interesting, such as Ruth Lichterman Teitelbaum training ENIAC's next operators, so that every sentence would support our argument. We also decided to paint the women as figures with blank faces in our illustrations, to show how history treated them before their names were recovered.
ENIAC was a technological innovation, but the women's work was an innovation in thinking, because they invented the process of programming. Its impact was the beginning of software. Its influence continued through their later careers. It also changed what the word "computer" means and who receives credit for building one.
Required written material
Annotated Bibliography
Primary sources
- U.S. War Department, Bureau of Public Relations. Press release on ENIAC. February 1946. Smithsonian Institution, Computer History Collection.The official announcement of ENIAC. We used it for the machine's specifications and to show whom the Army credited in 1946.
- U.S. Army. Photographs of ENIAC and its operators. 1946. University of Pennsylvania Archives.These photographs show the women at work on the machine, often without their names.
- Bartik, Jean Jennings. Oral history interview. Computer History Museum, 2008.A programmer's own account of learning and running ENIAC.
- Bartik, Jean Jennings. Interview by Janet Abbate, August 3, 2001. IEEE History Center Oral History #576. Engineering and Technology History Wiki, ethw.org.A full interview transcript. We used her own words about learning ENIAC from diagrams and about how women's work was rated.
- Bartik, Jean Jennings. Pioneer Programmer: Jean Jennings Bartik and the Computer That Changed the World. Truman State University Press, 2013.Bartik's memoir, which describes the women being left out of the 1946 celebration.
- U.S. Office of War Information. "More Women Must Work." Original artwork for a World War II poster. National Archives, NAID 7387548.Shows how the government urged women to take wartime jobs, the same push that brought women into the Army's computing work.
- Kennedy, T. R., Jr. "Electronic Computer Flashes Answers, May Speed Engineering." The New York Times, February 15, 1946, p. 1.The front-page story that introduced ENIAC to the public. It credits the inventors but not the programmers.
- Goldstine, Adele K. A Report on the ENIAC. Moore School of Electrical Engineering, 1946.The first ENIAC manual, written after the six had already learned the machine without one.
- U.S. War Department. TM 6-215: Abbreviated Firing Tables. 1941. Internet Archive.A real firing table from the war years, showing the kind of numbers human computers produced by hand.
- ENIAC Accumulator #2. Artifact. Smithsonian National Museum of American History, object nmah_334742.One of ENIAC's original panels.
- Goldstine, Herman H. The Computer from Pascal to von Neumann. Princeton University Press, 1972.An account by the Army's liaison to the project, which gives the engineers' and the Army's perspective.
Secondary sources
- Kleiman, Kathy. Proving Ground: The Untold Story of the Six Women Who Programmed the World's First Modern Computer. Grand Central Publishing, 2022.Our main secondary source on the six women and how they were forgotten.
- Haigh, Thomas, Mark Priestley, and Crispin Rope. ENIAC in Action: Making and Remaking the Modern Computer. MIT Press, 2016.A scholarly history that questions the "first programmers" label, which we used to show a different perspective.
- Grier, David Alan. When Computers Were Human. Princeton University Press, 2005.Background on the human computers who worked before electronic machines existed.
- U.S. Army Research Laboratory. ENIAC history summary. ftp.arl.mil/~mike/comphist.Our source for the contract, cost, dates and trajectory times.
- American Physical Society. "December 1945: The ENIAC Computer Runs Its First, Top-Secret Program." APS News, 2022.Our source for ENIAC's first problem for Los Alamos.
- Sydell, Laura. "The Forgotten Female Programmers Who Created Modern Tech." NPR, October 6, 2014.Our source for Jean Jennings Bartik's quotes about being left out. Because we found her words here, they count as a source within a source.
- "In Their Footsteps." American University Magazine.Describes how Kathy Kleiman discovered the women and the "refrigerator ladies" story.
Practice version made with AI for research and learning. Nolan and Felix will write and build the competition entry themselves on NHDWebCentral. Dashed boxes mark photographs and quotations still to be found and credited.