Women's legal right to vote was established in the United States over the course of more than half a century, first in various states and localities, sometimes on a limited basis, and then nationally in 1920.

The demand for women's suffrage began to gather strength in the 1840s, emerging from the broader movement for women's rights. In 1848, the Seneca Falls Convention, the first women's rights convention, passed a resolution in favor of women's suffrage despite opposition from some of its organizers, who believed the idea was too extreme. By the time of the first National Women's Rights Convention in 1850, however, suffrage was becoming an increasingly important aspect of the movement's activities.

The first national suffrage organizations were established in 1869 when two competing organizations were formed, one led by Susan B. Anthony and Elizabeth Cady Stanton and the other by Lucy Stone and Frances Ellen Watkins Harper. After years of rivalry, they merged in 1890 as the National American Woman Suffrage Association (NAWSA) with Anthony as its leading force. The Women's Christian Temperance Union (WCTU), which was the largest women's organization at that time, was established in 1873 and also pursued women's suffrage, giving a huge boost to the movement.Hoping that the U.S. Supreme Court would rule that women had a constitutional right to vote, suffragists made several attempts to vote in the early 1870s and then filed lawsuits when they were turned away. Anthony actually succeeded in voting in 1872 but was arrested for that act and found guilty in a widely publicized trial that gave the movement fresh momentum. After the Supreme Court ruled against them in the 1875 case Minor v. Happersett, suffragists began the decades-long campaign for an amendment to the U.S. Constitution that would enfranchise women. Much of the movement's energy, however, went toward working for suffrage on a state-by-state basis. These efforts included pursuing officeholding rights separately in an effort to bolster their argument in favor of voting rights.In 1916 Alice Paul formed the National Woman's Party (NWP), a militant group focused on the passage of a national suffrage amendment. Over 200 NWP supporters, the Silent Sentinels, were arrested in 1917 while picketing the White House, some of whom went on hunger strike and endured forced feeding after being sent to prison. Under the leadership of Carrie Chapman Catt, the two-million-member NAWSA also made a national suffrage amendment its top priority. After a hard-fought series of votes in the U.S. Congress and in state legislatures, the Nineteenth Amendment became part of the U.S. Constitution on August 18, 1920. It states, "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."