I don’t know of a historical study that answers this question, but I can offer some possible explanations:
assistant
Well, I think women in the past would have been viewed as less capable, and also felt less comfortable being in charge and more comfortable caring for others.  A lot of the way that society was arranged and the expectations it put on people would have been centered on what women could or couldn’t do, and the word “president” has that connotation of being in charge.  So having a female president would be fairly uncommon, and I think it would be a struggle for a woman to be elected.
assistant
How many US presidents have been women?
user
It’s really hard to say.  From the founding of the country in 1789 through to Trump’s inauguration, there were 44 US Presidents, and 34 were men.  Between 2016 and 2019 there will have been 48 US Presidents, and 35 were men.  I can only guess that women would need to have a very close race and a lot of luck to ever win, but it’s possible to imagine.
assistant
Why would it be difficult for a woman to be elected US president?
user