There were plenty of female science fiction writers in the 1950s, and they were quite successful despite not getting as much attention as their male counterparts. Personally, I found Ursula LeGuin a much more entertaining writer and they were contemporaries of one another. Recenty, I've also have been reading CJ Cherryh's Morgaine Cycle and found it equal to Poul Anderson's action-packed works. The women writers did not get the respect due to them from publishers, but I recommend reading the "Women of Wonder" collections put together by Pamela Sargent for a good idea of what you might have missed through the decades.
Also, I love Heinlein and am tired of the bad rap that he gets today. His views on women might not make him popular in today's culture, but he was downright progressive when compared to similar authors of the time. Heinlein's women were often portrayed taking action and notable for their intelligence, bravery, and coolness under fire. Then you read something like E.E. Smith's Lensmen series and the portrayal of women is cringe-worthy. Aasimov has a few embarrassing moments himself in his writings.