A constitutional amendment for women's suffrage (right to vote) was first introduced in Congress in 1878. It did not pass. But women's rights leaders fought for its passage for more than 40 years. Finally, in 1920, the 19th Amendment was added to the U.S. Constitution. It states that "the right of citizens of the United States to vote shall not be denied or abridged by the United States or by any State on account of sex." The passage of this amendment was the greatest victory of the women's rights movement.

After the Civil War (1861–65), women hoped that voting rights would be extended to both freed slaves and women. The 15th Amendment said, "The right of citizens . . . to vote shall not be denied . . . on account of race, color, or previous condition of servitude." Women struggled to have the word "sex" added to the amendment. But antislavery politicians worried that an amendment to grant black men suffrage would not succeed if women were included. So the word "sex" was left out. And in 1870, the 15th Amendment passed.

Women were more determined than ever to get the vote. But they differed in how to accomplish their goal. In 1869, two organizations were formed. Elizabeth Cady Stanton and Susan B. Anthony founded the National Woman Suffrage Association (NWSA). This group fought to pass a constitutional amendment to grant women the vote. The first women's suffrage amendment was put before Congress in 1878.

The second group was the American Woman Suffrage Association (AWSA). It was led by activist Lucy Stone. This group favored a more gradual approach. AWSA worked to win the right to vote state by state.

By 1890, women realized they were more likely to achieve their goal by working together. The two groups merged. The new organization was the National American Woman Suffrage Association (NAWSA). Elizabeth Cady Stanton served as its first president. Susan B. Anthony took over in 1892.

By 1900, women had made notable progress. They could vote in four states—Colorado, Idaho, Utah, and Wyoming. Many women attended secondary schools. Some went to college. Women also had property rights in many states.

Susan B. Anthony retired as president of NAWSA. Former teacher Carrie Chapman Catt stepped in as the new president. She was a brilliant organizer. She had, in her own words, a "voice like a foghorn." Catt brought new energy to the state campaigns. By 1915 a dozen states had granted the vote to women.

Other organizations also worked for women’s suffrage. Harriot Stanton Blatch, Elizabeth Cady Stanton's daughter, founded the Equality League of Self-Supporting Women. It held the first suffrage parade in New York City in 1910. The Woman's Christian Temperance Union (WCTU) also supported suffrage. So did a number of women in the growing labor movement.

No organization attracted as much attention as the National Woman's Party (NWP). Alice Paul and Lucy Burns founded this radical faction in 1913. Paul and a group of women picketed the White House. Many of them were arrested. Some went to jail.

These tactics brought attention to the movement. Not all of it was positive. Opponents claimed that granting women the vote would lead to the breakdown of society. One group opposed to women's suffrage was the liquor manufacturers. They feared women would use political power to restrict the sale of alcoholic beverages.

In 1912, some 15,000 women demonstrated by marching down Fifth Avenue in New York. In 1915, a similar march drew 40,000 people. Some women had stood on the sidelines, feeling that demonstrations were not "proper." Now they joined in. Men also offered support.

When the United States entered World War I (1914–18), women took over jobs left by men who joined the army. Women also served as nurses. They sold bonds to raise money. After the war, in 1918, another voting rights amendment was introduced to Congress. Many lawmakers felt it would be mean-spirited to vote "no" after all that women had done.

The House of Representatives held a dramatic session. Some legislators came despite illness. One was carried in on a stretcher. Another left his wife's deathbed—at her request—to vote for suffrage. The amendment squeaked through the House. It was defeated in the Senate that year. But in 1919 the Senate passed it.

Before the amendment could become law, it had to be ratified by three-fourths of the states. Women's groups in every state campaigned hard for ratification. On August 26, 1920, the 19th Amendment to the U.S. Constitution was adopted. At last, women had the right to vote. In November 1920, women for the first time proudly cast ballots all across America.