Charlotte Barnum (1860-1934) was a mathematician and women’s rights activist. She was the first woman to obtain a PhD in Mathematics from Yale University.
Even though she was rejected from Johns Hopkins University in 1890 on account of her gender, she persisted until she was allowed to attend lectures. She then moved to Yale, and obtained her PhD in 1935, opening new avenues for future female students. She worked for institutions such as the US Naval Observatory and the US Department of Agriculture.