Mary Kenneth Keller earned her place in computer science history: She helped develop BASIC as a grad student, and received a Ph.D. from the Computer Sciences Department at the University of Wisconsin in June of 1965, which tied her for the first doctorate in computer science ever. Irving C. Tang received his D.Sc. at Washington University in St. Louis the same month, which means that, briefly, half of all holders of doctorates in computer science were female.
And, yes, to add the oddball twist to this story: Keller was a nun, a Sister of Charity of the Blessed Virgin Mary, an order dedicated to education. Keller went on to chair the Clarke College CS department for twenty years.