Few, if any, of my classmates shared my fascination with the Mark I Computer that was on display in our university’s Science Center. It is hard to blame them. Towering at 8 feet and filled with rotary switches, crystal diodes, and tangled wires, the Mark I resembles a prop from a science fiction movie rather than a computer the U.S. Navy once used. In its prime in the 1940s, the Mark I was one of the most powerful supercomputers on Earth; today, the smartphone we carry in our pockets would put it to shame. Yet, neither the smartphone nor the operating system that powers it would be possible without the early mainframes like the Mark I or the computer science pioneers who operated them. Many of those pioneers were women.