I agree that the women in Little House were strong in their own ways...they had to be, as they were living out in the middle of no where.
However, I disagree on time period being the main factor in how females are portrayed. Look at Disney's fairy tales, where all the girls are "waiting to be rescued by their prince" or something along those lines. Leaving little girls all over the world believing that the main goal of a woman is to find a man. Too many books, even newer ones, are written to show the boys as more competent than the females, even if the females are gaining ground. Little girls and young women ought to have books available to them that portray a woman as more than someone who needs a man.
Of course, I am rather independent myself, as a female engineer. So I tend to be an advocate of equality...especially for children. (And no, I'm not a feminazi).