Women in the United States gained the constitutional right to vote with the ratification of the 19th Amendment. This amendment was passed by Congress on June 4, 1919, and ratified on August 18, 1920. It legally guaranteed women the right to vote by declaring that the right of citizens to vote could not be denied or abridged on account of sex. Before the 19th Amendment, some states and territories had already granted women voting rights. For example, Wyoming granted women suffrage in 1869, Utah in 1870, Colorado in 1893, and several other states followed through the early 20th century. However, the 19th Amendment was the first nationwide legal guarantee of women's suffrage. Despite the amendment, in practice, many women of color, particularly in the South, faced barriers due to discriminatory laws until more protections like the Voting Rights Act of 1965 were established. In summary:

• Some women could vote in certain states and territories from as early as 1869.
• The 19th Amendment, granting women the right to vote across the US, was ratified on August 18, 1920, ensuring voting rights regardless of sex at the national level.