The first organized movement aimed at gaining rights for American women effectively began in July 1848, with the convention organized by Elizabeth Cady Stanton and Lucretia Mott at Seneca Falls, New York. Attendees signed the Declaration of Sentiments, which affirmed women’s equality with men, and passed a dozen resolutions calling for various specific rights, including the right to vote.

Although the early women’s rights movement was linked to abolitionism, passage of the 15th Amendment in 1870 angered some women’s rights leaders who resented Black men being granted suffrage before white women. Similarly, the women’s suffrage movement also largely marginalized or excluded Black feminists like Sojourner Truth and Ida B. Wells. Though ratification of the 19th Amendment in 1920 fulfilled the principal goal of feminism’s first wave—guaranteeing white women the right to vote—Black women and other women of color faced continued obstacles until passage of the Voting Rights Act of 1965.

In 1963, Betty Friedan published The Feminine Mystique, which argued that women were chafing against the confines of their roles as wives and mothers. The book was a massive success, selling 1.4 million copies in three years and launching what became known as the second wave of feminism. Inspired by the civil rights movement and protests against the Vietnam War, second-wave feminists called for a reevaluation of traditional gender roles in society and an end to sexist discrimination.

Feminism—or “women’s liberation”—gained strength as a political force in the 1970s, as Friedan, Gloria Steinem, Bella Abzug and others founded the National Women’s Political Caucus in 1971. High points of the second wave included passage of the Equal Pay Act and the landmark Supreme Court decisions in Griswold v. Connecticut (1965) and Roe v. Wade (1973) related to reproductive freedom. But while Congress passed the Equal Rights Amendment in 1972, a conservative backlash ensured it fell short of the number of states needed for ratification.

Like the suffrage movement, second-wave feminism drew criticism for centering privileged white women, and some Black women formed their own feminist organizations, including the National Black Feminist Organization (NBFO). Despite its achievements, the women’s liberation movement had begun to lose momentum by 1980, when conservative forces swept Ronald Reagan to the White House.

While the advances of second-wave feminism had undoubtedly achieved more equality and rights for women, the movement that emerged in the early 1990s focused on tackling problems that still existed, including sexual harassment in the workplace and a shortage of women in positions of power. Rebecca Walker, the mixed-race daughter of second-wave leader Alice Walker, announced the arrival of feminism’s “third wave” in 1992, while watching Anita Hill testify before the Senate Judiciary Committee about her accusations of sexual harassment against Supreme Court nominee Clarence Thomas. That same year, dubbed the “Year of the Woman,” saw an unprecedented number of women elected to Congress.

Embracing the spirit of rebellion instead of reform, third-wave feminists encouraged women to express their sexuality and individuality. They argued it should be women, themselves, who decide how they wanted to present to the world. Some embraced a more traditionally feminine style of dress and grooming, and even rejected the term “feminist” as a way of distancing themselves from their second-wave predecessors. “Riot grrl” groups like Bikini Kill, Bratmobile and Heavens to Betsy brought their brand of feminism into popular music, including songs that addressed issues of sexism, patriarchy, abuse, racism and rape.

Third wave feminism also sought to be more inclusive when it came to race and gender. The work of scholar and theorist Kimberlé Crenshaw on the concept of “intersectionality,” or how types of oppression (based on race, class, gender, etc.) can overlap, was particularly influential in this area. Third-wave feminists also drew on the work of gender theorist Judith Butler, including support for trans rights in this type of intersectional feminism.

Though fourth wave feminism is relatively difficult to define—as some people argue it’s simply a continuation of the third wave—the emergence of the Internet has certainly led to a new brand of social media-fueled activism. Launched by Tarana Burke in 2007, the #MeToo movement took off in 2017 in the wake of revelations about the sexual misconduct of influential film producer Harvey Weinstein.

In addition to holding powerful men accountable for their actions, fourth-wave feminists are turning their attention to the systems that allow such misconduct to occur. Like their predecessors in the feminist cause, they also continue to grapple with the concept of intersectionality, and how the movement can be inclusive and representative regardless of sexuality, race, class and gender.