Barbara Liskov is the first woman in the United States of America that obtained a Ph.D. from a Computer Science department, in 1968. However, this isn't by any chance her greatest achievement.
She's the creator of the CLU programming language, a language created in the mid-70s, that we would find crufty and ugly nowadays, but that with its strong emphasis in abstraction, the use of clusters (basically equivalent to what we call classes today) and iterators, was to become the rock foundation of Object Oriented Programming.
Apart from that, she worked in the design of a timesharing operating system, called Venus; designed another programming language, called Argus, that was oriented to distributed applications, and also set the foundations for much of what is currently done as distributed computing.
Aged 70, she's currently still working at MIT, as the leader of the Programming Methodology Group, researching ways to tolerate byzantine faults.
All in all, what I find the most inspiring of all her life, is the fact that she was able to pursue her career, working on a new way of creating programs, while she was also a wife and a mother; and that today, aging 70, she's still researching, leading a group, and working towards making computing better.