Cannon was born in 1863, and her family believed in education for everyone, not just for men. When Cannon’s teachers suggested she go on to college, her father selected the recently opened Wellesley College in Massachusetts for her.

Cannon grew up with her mother’s love of the stars. Mary Cannon found stargazing a relaxing break from raising a large family.

Moving from Delaware to Massachusetts, Cannon wasn’t ready for the severe winters. Much of the time she was sick, and this led to permanent hearing loss. Professor Sarah F. Whiting, who taught physics, astronomy and other sciences, helped Cannon develop her love of astronomy. Later Whiting gave her a job as her assistant. Cannon continued studying astronomy at nearby Radcliffe because it had access to Harvard’s observatory.

Sometimes fate has funny turns. For Cannon, a Harvard professor’s anger at his assistant was to be a great break. The professor said his maid could do a better job at the observatory than the assistant, and he hired the maid to prove it. The maid did much better. This led to Cannon eventually being hired as an assistant at the observatory.

Cannon’s work included developing a system to classify the different stars. That system is still in use today.

Over the years, Cannon’s ability to recognize and categorize the stars would grow as her work continued at Harvard. She received many awards for her work. She was the first woman awarded an honorary doctorate by Oxford University in England.