equal to men and that gender differences were a social construct, not "natural" and "innate," flew in the face of thousands of years of received wisdom. The idea that women should have equal political, legal and economic rights challenged the way society had been organized for millennia. It doesn't get more counter-cultural than that.

Feminism contributed to the countercultural movement, as the counterculture was meant to bring awareness to groups that had been oppressed and marginalized by mainstream society up to that time. Women started to push for more rights in the family, such as the right to decide when and how many children to bear. This led to an increase in the availability of contraceptives for women and abortion. Women also wanted greater equality in the workplace. Women wanted the same pay as men for doing the same amount of work. Women also pushed to be included in scholarship athletics through Title IX.

These attitudes were seen in the media and thus cemented the women's movement within the counterculture. Television shows started to portray strong female leads who held fulfilling jobs. Female musicians such as Janis Joplin became the idol of many. Billie Jean King's success as a tennis player helped to popularize women's athletics. The feminist movement allowed women to demonstrate strength, and it became socially acceptable and encouraged.

Feminism struck at the heart of traditional western culture by calling into question its most fundamental relationships. They emphasized, and continue to emphasize, that gender roles are social constructions, not necessarily biological facts, and that these social constructions amount to a system of oppression. Feminists argued for full political and social equality for women, and this entailed fundamental change in the jobs that women were expected to do as well as the nature of relationships within the home. The questions they raised about gender also paved the way for entirely new movements, most notably the movement for gay rights. Many of the core issues they brought to the forefront, including reproductive rights, pay equality, and equality of educational opportunities, have become mainstream ideas in western society.

The whole idea of the counterculture was that it was supposed to reject the values of mainstream American culture.  During those days, male dominance was one of the values of mainstream American culture.  Feminism, then, contributed to the counterculture by offering a challenge to the male-oriented mainstream.

This was done in a number of ways.  Two of them were women's rights/liberation and the "sexual revolution."  The issue of women's rights was a legal one.  Women were pushing to be accorded equal legal status with men.  The sexual revolution was more of a social thing.  The idea that women had to be chaste while men could be sexually active was a longstanding double standard.  Helped by "The Pill" women started to challenge this idea that they were not supposed to be as sexual as men.  In these ways (and in others) feminism helped to challenge the values of mainstream America.