On the 50th anniversary of the Apollo 11, it’s too simple to just celebrate the men who got the chance to step on the moon. The fact of the matter is that without the work of female mathematicians, space travel would have never been possible.

Long before NASA was created, groups of female mathematicians have been working at the Harvard Observatory and the Royal Observatory Greenwich since the late 1800s. These women were responsible for performing the complex mathematical calculations that would ultimately be responsible for sending astronauts to the moon at a time where electronic computing systems had yet to be invented.

Later in the 1950s and early 1960s after NASA was formed, engineer Katherine Johnson was credited for designing the trajectory that would allow John Glenn perform his record-breaking orbit around the Earth in 1962—with Johnson being awarded the Presidential Medal of Freedom in 2015.

Since then, thousands of women have filled the positions at NASA that have led us deeper into space, with the next obvious step being that a woman should step foot on the moon. As we celebrate the anniversary of Apollo 11, we must also remember the many women who brought us to the moon.