Standing Before the MANIAC I: Klára Dán von Neumann, a Pioneer in Coding

This week, I’ve been reading The Maniac by Benjamin Labatut. It’s a brilliant deep dive into the world of early computing, with all its mad geniuses and improbable breakthroughs.

But—and it’s a big but—where are the women? They’re mentioned in The Maniac, of course, but their stories feel secondary, like they’re just passing through history. Take Klara Dán von Neumann, for instance. She’s noted as a figure skater, as someone who ended up coding computers almost by coincidence, and as a person juggling everyday challenges like arguing with her husband over a garage door. What’s missing is the emphasis on her contributions to computing—work that helped shape the very foundation of modern programming. It’s not that women didn’t exist in this world; it’s that they didn’t always get the same opportunities as men, and their achievements are too often overshadowed by trivial anecdotes.

Klara Dán with her husband John von Neumann and their dog (Photo: Alan Richards)

Klara Dán von Neumann

Let’s talk about Klara Dán von Neumann.

Born in Budapest in 1911 into a wealthy Jewish family, Klára grew up in a vibrant cultural environment. Her family’s villa was a hub of social and intellectual gatherings where politicians, artists, and intellectuals mingled. Her early life was filled with luxury and culture, but her first passion was figure skating. By her teenage years, she was a national champion, showcasing the discipline and precision that would later define her work in computing.

Her personal life was colourful and complex. Married four times, her third marriage to mathematician John von Neumann proved pivotal. Before meeting John, Klára had already experienced a tumultuous first marriage to Ferenc Engel, a gambler, and a second to Andor Rapoch, a banker. Her encounter with von Neumann was serendipitous—the two met at a roulette table in Monte Carlo, an apt setting for a woman whose life would be defined by calculated risks and numbers.

Klára and John’s marriage brought her to Princeton, where their home became the site of legendary parties, blending intellectual discourse with lavish entertainment. As the onset of World War II loomed, Klára returned to Hungary in a daring attempt to convince both her family and John’s to flee Europe. Despite the mounting danger, she managed to get them out, demonstrating remarkable courage and determination.

Her departure was nothing short of dramatic. Von Neumann, concerned for her safety, wrote to her pleading, “For God’s sake do not go to Pest, and get out of Europe by the beginning of Sept! I mean it!” Klára heeded his warnings just in time, sailing from Southampton on 30 August 1939. Germany invaded Poland the very next day, marking the beginning of the war. Though she escaped safely, the emotional toll was profound. Her father, unable to adjust to life in America, tragically took his own life later that year, plunging Klára into a deep depression. 

Klára and John’s marriage brought her to Princeton, where their home became the site of legendary parties, blending intellectual discourse with lavish entertainment. With the onset of World War II, Klára returned briefly to Hungary to help her and John’s families escape Europe, showcasing her resourcefulness and determination.

After the war, Klára joined John in Los Alamos, a bustling hub of scientific innovation. The social hub of Los Alamos, the post exchanges, was where she could often be found, smoking Lucky Strikes and meticulously working on strings of numbers and symbols. This work was no mere pastime—it marked her entry into the world of computing.

The Mathematical Analyzer, Numerical Integrator And Computer did the calculations for ”Project Mike,” which produced the first hydrogen bomb. It was similar to the other IAS-inspired machines, though all were different enough that they could not exchange programs. (Photo by © CORBIS/Corbis via Getty Images)

Klára’s work with the ENIAC and later the MANIAC I was pivotal. Despite having no formal training in mathematics, she played a key role in programming some of the first complex programs ever to run on a modern computer. Her meticulous coding translated complex mathematical problems into machine-readable language, including one of the earliest computerised weather simulations and programs for nuclear simulations. These programs were critical for advancing meteorology and refining nuclear weapons.

One of her most notable achievements was writing and overseeing code that simulated neutron paths in atomic bombs, contributing to the development of more efficient nuclear weapons. Her 800-command program, which included early examples of closed subroutines, was groundbreaking. While the Manchester Baby is often credited with being the first stored-program computer, Klára’s program ran months earlier, solving far more complex problems.

A Life of Triumph and Tragedy

Klára’s life was marked by incredible contributions and personal struggles. The pressures of working in a male-dominated field, combined with personal tragedies like the loss of her father and a late-term miscarriage, weighed heavily on her. Her relationship with von Neumann was intellectually stimulating but often emotionally distant due to his demanding career.

After von Neumann’s death in 1957, Klára married physicist Carl Eckart and moved to La Jolla, California. However, her struggles with depression persisted. In 1963, at the age of 52, she tragically took her own life, leaving behind a legacy that is only now being fully appreciated.

Why Klára’s Story Matters

Klára Dán von Neumann’s story reminds us that history is often written with gaps—and the contributions of women in early computing are some of the most glaring omissions. She wasn’t just a typist or someone following instructions; she was a pioneer, navigating an unfamiliar field and helping shape the future of programming. Her programs demonstrated the immense potential of digital computers and paved the way for countless innovations we now take for granted.

But Klára’s life wasn’t just about codes and computers; it was also about resilience, creativity, and complexity. From her glamorous beginnings in Budapest to her groundbreaking work in Los Alamos, she lived a life full of contradictions: privilege and loss, brilliance and insecurity, triumph and tragedy. Her achievements came despite the barriers of her time, and her legacy continues to ripple through the tech world today.

So now, when I see the MANIAC I, I don’t just see a historical relic. I see Klára. I see the scribbles on paper that became the building blocks of modern computing. I see a woman who refused to be defined by the limitations of her era and whose work remains a quiet, yet vital, part of our digital lives.

Further Reading

If you’d like to learn more about Klára Dán von Neumann and her extraordinary life, I highly recommend the book Klara and the Bomb. It offers a deeper dive into her contributions to computing and the challenges she faced, painting a vivid portrait of a woman who truly changed the course of history.