When the 19th Amendment became law 100 years ago, women could no longer be barred from the polls because of their sex. Yet for Black women, ratification marked not the end but the beginning of a movement for voting rights. The intimidation tactics, violence and Jim Crow laws that kept Black men from the polls would deny Black women their votes for the next four-plus decades. Their struggle for equality, until passage of the Voting Rights Act in 1965, holds lessons about the need to remain ever vigilant against voter suppression efforts.

In the months before Tennessee’s ratification made the 19th Amendment law, those Southern lawmakers who supported women’s votes did so with the understanding that Black women’s access to the ballot box would not be protected. The amendment’s language did not prohibit states from continuing to impose poll taxes, literacy tests and “understanding clauses,” nor did it require them to curb the intimidation and violence directed at Black women.

Knowing this, Black women organized. Citizenship workshops and suffrage schools opened in church halls and YWCA meeting rooms, and Black women guided one another through the maze of voter registration requirements. Hoping for relative safety in numbers, women in many places turned out in groups to register. Some succeeded in getting their names on the rolls in 1920, but many, especially in Southern states, did not. Exercising their political influence would, perhaps counterintuitively, require more than a constitutional amendment.

Hallie Quinn Brown, leader of the National Association of Colored Women — whose 300,000 members made it the nation’s largest political organization of Black women — understood that the 19th Amendment needed teeth. Aiming to win federal legislation that would override state-level obstacles to the polls, she sought an alliance with Alice Paul and the National Woman’s Party. But Paul declined and the National Woman’s Party followed, leaving Black women to carry on the fight for ballot access by new terms — ones that linked their quest with the goals of the growing civil rights movement.

The battle for voting rights had many fronts. In federal courts, the NAACP argued that the Constitution did not countenance racism and that the 15th Amendment, ratified in 1870, ensured Black Americans’ access to the polls. In its 1915 decision in Guinn v. United States, the Supreme Court struck down “grandfather clause” exemptions to literacy requirements for voting rights, as they discriminated against Black people whose formerly enslaved grandfathers could not vote. It was 1944 before Smith v. Allright overturned a Texas law that excluded Black voters from primaries. Outlawing poll taxes required its own constitutional amendment, the 24th, which was not ratified until 1964. It was another year before the Voting Rights Act ended disenfranchisement.