Many Americans think men and women are already equal under the law. But these 24 simple words have been kicking around for 169 years without being ratified as an amendment to the Constitution:

Equality of rights under the law shall not be denied or abridged by the United States or by any state on account of sex.

Nearly all other Constitutions have incorporated words like this. Only the United States is lacking an Equal Rights Amendment. “Women were left out of the Constitution more than 200 years ago. Almost 100 years ago, just after women finally got the right to vote, the ERA was introduced by Alice Paul to give women all other equal rights. We are way behind the rest of the world, where most countries have constitutional guarantees of sex equality,” says Jessica Neuwirth, president of the ERA Coalition. “It’s time to put women in the Constitution once and for all.” As we watch women’s rights being rolled back again and again we realize that without a place in the Constitution we will never be able to safeguard the gains we make.

In the 1930s, when my mother was an art student at the National Academy of Design, the president of the academy told her that though she was the best artist in her class she would not win the Prix de Rome. When she asked why, he said, “Because you’ll have babies and waste your talent.” I first heard this depressing tale when I was only 9—which perhaps explains my passionate life-long feminism. I understood at a very young age that it was my responsibility to make the world better for women.

I went to a wonderful women’s college—Barnard—where women’s excellence was nurtured and celebrated, but as soon as I got to graduate school across the street I realized that the wider world was not the same. For the first time in my life I experienced the condescension that all my fellowships and poetry awards could not erase. As I matured as a writer, I saw clearly how much prejudice there was against women.

It’s true, of course, that we finally got the vote. And the vote is important, but as feminists have always understood, it is not sufficient to guarantee equality. We also need an Equal Rights Amendment to make sure that our rights are incorporated in and protected by the Constitution so they can never be taken away. Happily a new generation of feminists—both female and male—has begun to understand this and is ready to fight for complete equality.

The concept of the “rights of man” arose during the Enlightenment and gave violent birth to the American and French Revolutions, in 1776 and 1789 respectively. Naturally, there were women who responded to that concept by pointing out their lack of rights. In 1792, Mary Wollstonecraft’s Vindication of the Rights of Women argued that women as well as men needed rights. A contemporary of Thomas Jefferson, Thomas Paine, and the founders of the American Experiment, Wollstonecraft, like most 18th-century women, lived a life sorely in need of rights. Married to William Godwin, mother of Mary Godwin-Shelley, Wollstonecraft died in childbirth, the fate of so many women of that era. The life of the daughter she left behind, who married Percy Shelley when she was 19, was also tragic. Mary Shelley lost children in infancy and her poet husband drowned off the coast of Italy. She left the world her great fantasy, Frankenstein, which has kept publishers and movie producers in business ever since.

When I first began to study the history of women’s rights, I was astounded by the number of talented women who died in childbirth and the fact that those who survived were traumatized by the frequent loss of their babies. How could women have created under these circumstances? And yet they did. It’s not surprising that for many women spinsterhood was the remedy for constant pregnancy and perpetual mourning. Learning about the lives of these women, you can’t help but be inspired by their fierce energy and tenacity.

The struggle for women’s vote was won in infinitesimally small steps both in England and America. Curiously, British women got the right to stand for Parliament in 1918, before they even had the vote. American women won the right to vote in 1920 and British women finally won it in 1928. Women’s struggle for suffrage started as a polite debate, but activists soon realized that they would have to battle fiercely to achieve anything—and many died before they saw success.

Alice Paul, who fought for suffrage in the United States and the UK, was a Quaker who went to England to study social work and there met Christabel Pankhurst, Emmeline’s daughter. Radicalized by her experience in Britain, she came to understand that American suffrage would only come after a similar great struggle. Founder of the National Women’s Party in America, she was among the first who recognized that without an Equal Rights Amendment, suffrage was not a complete victory. Women had to be protected by the Constitution. Since they were not, a constitutional amendment was necessary.

First, suffrage had to be won. In 1848, Elizabeth Cady Stanton and Lucretia Mott convened a meeting of 300 women and men to demand justice for women at the first women’s-rights convention in Seneca Falls. A proposal to push women’s right to vote was passed after Frederick Douglass and Elizabeth Cady Stanton made impassioned speeches. It’s important to know that Frederick Douglass, the only African American present, was a staunch advocate of female suffrage.

After the end of the Civil War, Stanton, Susan B. Anthony, and Sojourner Truth fought to have women included in the new constitutional amendments giving rights to former slaves. The 14th Amendment defined citizens as “all persons born or naturalized in the United States” and guaranteed equal protection of the laws, but when Susan B. Anthony went to the polls in 1872 and cast a ballot in the presidential election, she was arrested, tried, and convicted of a crime. In 1875 the Supreme Court in Minor vs. Happersett said that, while women may be citizens, all citizens were not necessarily voters, and therefore states were not required to let women vote. Elizabeth Cady Stanton and Susan B. Anthony continued to campaign for a voting-rights amendment for women, but they both died before achieving their aim.

Under the direction of Carrie Chapman Catt, the National Women’s Suffrage Association—originally created by Elizabeth Cady Stanton and Susan B. Anthony—became important as a lobbying force from 1900 to 1920. Meanwhile, Alice Paul developed the National Women’s Party into a small radical group that by 1916 had begun the process of making the fight for women’s right to vote visible and inevitable. In 1919, the 19th Amendment affirming the right of women to vote had been ratified by about half the states. Then came serious resistance from states rights’ advocates, the liquor lobby, and a number of women who believed that the amendment would threaten the family. (I am always astonished by women who question their own right to power—but there have been many.)

But the anti-suffrage forces did not prevail. The 19th Amendment, providing for female suffrage, was passed by Congress on June 14, 1919. In the summer of 1920, Harry Burn, a 24-year-old state legislator in Tennessee, switched his vote from no to yes because his mother had encouraged him to “vote for suffrage.” Finally on August 26, 1920, the right of women to vote was confirmed. We celebrate women’s suffrage on Women’s Equality Day every August 26.

But as any woman can tell you—the vote was not enough. Customs, prejudices, and sexism do not disappear so fast.

Alice Paul foresaw all of this. She realized that unless we had an Equal Rights Amendment, we would never be able to insure our rights to claim equal protection under the law. And she was right. The struggle for the ERA began in 1923, on the 75th anniversary of the 1848 Women’s Rights Convention. Alice Paul introduced something she called the “Lucretia Mott Amendment.” It’s so simple and appropriate that it’s hard to anticipate any objection: Men and women shall have equal rights in every place in the United States that is subject to its jurisdiction. It took until 1940 for the Republican and Democratic parties to add the ERA to their platforms. The proposed Amendment now read: “Equality of rights under the law shall not be abridged by the United States or by any state on account of sex.”

In earlier decades, the ERA’s prospects seemed promising. In 1972, the proposed amendment was sent by Congress to the states for ratification. But opposition ramped up not long after. Fundamentalist religious groups opposed it, as did businesses that were afraid that if it passed, women would demand higher pay.

But the mechanism of passing a constitutional amendment is, perhaps intentionally, extremely cumbersome in the United States. Ratification by three-quarters of the states (38) is required. So far 35 states have ratified the ERA, but five states have rescinded their ratifications, so eight more are required. As becomes evident when you talk to Americans about the ERA, this long and twisting path has confused many people about what it would take to finish the job. Some lawmakers claim that we only need two more states to ratify, but most agree that rescinded ratifications don’t count.

Whenever ratification seems near, another obstacle is invented. My generation of second-wave feminists couldn’t turn on the TV without seeing the odious Phyllis Schlafly talking about how we’d all have to use the same bathroom if the ERA was passed. Idiotic as this may seem to us today, bathroom fears were often introduced in puritanical America. Even today the bathroom issue is raised to deny rights to transgender people. Phyllis Schlafly may be dead, but right-wing, anti-woman propaganda is not.

Despite this, millennial women and men have taken up the fight for the ERA because they understand that if we are not protected in the Constitution our rights can always be taken away.

“I was first made aware of the Equal Rights Amendment when I was 14 and blessed with a dynamic high-school English teacher,” writes Erin Vincent, activist and author of Grief Girl. I met Erin at one of my book signings in California, and we have maintained correspondence since. Her teacher was a radical feminist who got up on stage and belted out the song “You Don’t Own Me” during a talent-night fundraiser. Erin adds, “It’s not enough to take a selfie while wearing a this is what feminism looks like T-shirt. Your pink pussy hat is not going to protect you if there is no law explicitly protecting your rights.”

Laura Durnell, another young writer and activist who studies women’s literature, says, “My high school…never fully addressed women’s history. We devoted half a day to the 19th Amendment, but the suffrage movement wasn’t even discussed.” Inspired to research the history of the ERA in her home state of Illinois, she discovered that male Republicans in the Illinois state legislature had defeated it.

“As young women we got many mixed messages,” she writes. “Promised by our elders that we could be successful in every way and support ourselves and our children, we never learned how weak the underpinnings of our freedom were.”

And now we still don’t have an Equal Rights Amendment in our Constitution. How can we change this depressing fact? Let’s listen to Ruth Bader Ginsburg who understands, perhaps more than any historian, how the law affects women:

[T]he equality principle…is not in the original Constitution.… The equal-protection clause shows up in the Fourteenth Amendment, which is a restriction on what states can do.… The Court incorporated an equality principle into the due-process clause of the Fifth Amendment…. But I suppose the best reason is, if you look at any Constitution that has been written since 1950, you will find in it a statement that men and women are equal before the law. So, I have three granddaughters. I would like to be able to take out my pocket Constitution and say that the equal-citizenship stature of men and women is a fundamental tenet of our society—like free speech. The woman’s equal right to do whatever her talent and hard work enable her to do, and I’d like that to be in the constitution. [Emphasis added.]

And so would we all like “to be in the Constitution.” We’d like it for our daughters, our granddaughters and also for our sons and grandsons. Laws are important. They enshrine beliefs and make them actionable. They tell us what our society stands for. We stand for equal rights: our Constitution must reflect this.

Editor’s Note: This article first identified Jessica Neuwirth as president of Equality Now. In fact, she is president of the ERA Coalition. The text has been corrected.