The year 1917 was highly consequential for the suffrage movement. Having lost the chance to defeat the reelection of President Woodrow Wilson, who had initially been lukewarm toward suffrage, activists set their sights on securing voting rights for women by the 1920 presidential election.

One wing of activists began a daily picket of the White House, the first in American history. Another organized a lobbying campaign to win Congressional votes. Then, in April of that year, the United States entered World War I, and whatever political will that had been building for women’s enfranchisement evaporated.

Still, suffragists were not deterred. One of the most powerful weapons they had was the four million women already empowered to vote by their state constitutions. These women could cast ballots in all elections, up to the federal level, including for congressional representatives and for president. All of these “suffrage states” were still west of the Mississippi, but in November, suffragists won the richest state suffrage prize, New York.

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New York was the wealthiest, most politically powerful state in the union. Now its 46-person delegation, the largest in Congress, was answerable to female as well as male voters. Just two months later, the lone Congresswoman, Jeannette Rankin of Montana (a state where women could vote) presented the bill authorizing a constitutional amendment to the House of Representatives. Amendment legislation requires the support of two-thirds of each house, and the bill passed without a vote to spare.

Now it was on to the Senate. Historically the more supportive of the two chambers, suffragists expected a quick victory there. Carrie Chapman Catt, president of the National American Woman Suffrage Association, even bought a new dress for the occasion. Even a new and deadly opponent, the 1918 flu pandemic, did not keep suffragists from pressing forward. Despite the momentum, Southern Democrats and conservative Republican senators managed to stop the bill.

Election results were what finally shifted the political ground. Once the war was over, the nation was in the mood for a change and the November 1918 midterms turned over control of Congress to the Republican Party. At the last minute, a southern Democratic Senator tried to amend the bill to limit the vote to white women, but this failed. Finally, in June 1919, in one of its first legislative acts, the new Congress passed the bill and the suffrage amendment went out for ratification. Catt called Congressional passage an “electric touch that sets a vast and complicated machinery in motion.”

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Ratification is the final and steepest obstacle to amend the constitution. A majority of legislatures in three quarters of the states must vote in favor. At least six constitutional amendments—most notably the Equal Rights Amendment—have passed through Congress but failed ratification. The woman suffrage amendment had the advantage of well-organized, dedicated suffrage supporters in every state, but the anti-suffrage movement was equally energized.

Ratifications began quickly—within four months, 17 states had acted—but then slowly ground to a halt. States like Colorado, Wyoming and South Dakota, where women had been voting for decades, saw no rush to enfranchise women in the rest of the country. In Washington State, where women had been full voters since 1911, the governor resisted calling a special session of the legislature to consider the suffrage bill, but finally, in March, nine months after Senate passage, he relented, and Washington became the 35th state.

Where would the 36th state ratification come from? In Connecticut and Vermont, conservative Republican governors refused to call their legislatures into session. All eyes turned to the South, where most states were controlled by white supremacist Democrats. By July, four months after the ratification in Washington State, prospects for ratification from a 36 state were gloomy, and suffragists were becoming desperate.

Finally, Tennessee, a rare southern state with two parties, came through with the tie-breaking vote. A young Republican legislator cast the deciding ballot. Eight days later the U.S. Secretary of State announced that the 19th Amendment had officially become part of the Constitution.

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Suffragists had nine weeks to get women registered to vote. While there is no way to know exact numbers, it is generally accepted that one-third of eligible women voted in the 1920 election (versus two-thirds of men).

The era of woman suffrage was over. The era of women working their way up and through the political process had begun. As one suffragist put it, it was “the dawn of woman’s political power in America.”

Ellen DuBois is Distinguished Research Professor in the History Department of UCLA and author of numerous books on the history of woman suffrage in the US, including, Suffrage: Women's Long Battle for the Vote.