As Senate Democrats push to extend federal protection of voting rights, bills to restrict citizens’ access to the vote — many based on models produced by the conservative Heritage Foundation — have been introduced in 43 states. On Thursday, Georgia enacted a law that limits voters’ options and makes it easier for the state legislature to interfere with election results. The current absence of strong federal protection for voting rights resembles the United States before the Civil War and reminds us of why Americans changed the Constitution to protect individual rights during Reconstruction.

From the nation’s founding through the Civil War, the states had virtually unchallengeable power to define the status and rights of their residents. Slavery was only the most extreme example. Northern states such as Massachusetts and Pennsylvania chose to abolish slavery in the years following independence from Britain, but across the Southern tier of states, legislatures perpetuated slavery and codified it in law. Congress admitted new slave states to the Union, putting its imprimatur on states’ “right” to legalize slavery and to people’s right to hold Black people in bondage, denying them rights that many considered fundamental to personhood.

Beyond slavery, all slave states and some free states placed strictures on the basic rights of free African Americans. After joining the Union as a free state in 1803, for example, Ohio adopted laws that required free African Americans who wanted to live in the state to prove their freedom and register with local officials. Laws forbade them from testifying in court cases involving White people, and barred Black children from public education. Ohio’s constitution granted voting rights to White men only. By contrast, Massachusetts placed no racial restrictions on men’s right to vote and had no racist or testimony residency laws. It did, however, bar interracial marriage and prohibit Black men from serving in the state militia.

Meanwhile, no slave states permitted Black men to vote and only a handful of free states did.

As a consequence of this patchwork of race and rights, the antebellum struggle for racial equality looked different in every state. In Ohio, Black activists pressed for repeal of the “Black laws” that marginalized them and made them vulnerable to exploitation and violence by White people.

Yet, Black Ohioans were just 1 percent of the state population, and Black men could not vote. As a result, there was little they could do about the laws besides organize, petition the state legislature for justice and call on White neighbors to see the world from their eyes and do what was right. In 1843, a convention of Black men called on White Ohioans to recognize the injustice of the laws, insisting that the state government’s policy toward them was “utterly at variance” with the promises of the Declaration of Independence.

Residents of Atlantic Coast states rallied around different issues. Northern Black men often worked as sailors on ships engaged in the intercoastal trade, and their work took them to Southern ports such as Charleston, S.C., and New Orleans. Driven by fears that Black sailors carried ideas about freedom and would provoke uprisings of the enslaved, however, Southern states had adopted laws requiring free Black sailors to report to jail, remain on their ships or carry passes proving their freedom. Authorities regularly subjected Black sailors to arrest and abuse, and those who landed in jail could be sold into slavery if they didn’t find a way to get released — despite the fact that they were free.

In New York and Massachusetts, activists and eventually state legislatures searched for ways to protect Black sailors who sailed out of northern ports. The legislatures denounced Southern abuses and appropriated funds for securing Black prisoners’ release. But on the larger question — how could Southern officials throw Black northerners in jail simply for the “crime” of being Black? — they found no recourse in Congress or in the federal courts.

The Reconstruction amendments to the Constitution — the 13th, 14th and 15th — were designed to set the nation on an entirely new footing, by curtailing some of the traditional prerogatives of the states. The amendments empowered Congress to secure, across the entire nation, freedom itself, basic civil rights for all people and the right to vote regardless of “race, color, or previous condition of servitude.”

Tragically, however, the 14th and 15th amendments went largely unenforced for nearly a century thanks to narrow interpretations by the Supreme Court, a general lack of will in Congress or, when some in Congress did seek to protect African Americans’ voting rights or make lynching a federal crime, an inability to overcome entrenched Southern power.

Everything changed with the Civil Rights Act of 1964 and the Voting Rights Act of 1965 (VRA), which passed after decades of grass-roots activism and the creation of a broad bipartisan coalition in Congress capable of overcoming both the power of Southern committee chairs and the potency of the Senate filibuster. This legislation reinvigorated the guarantees of the 14th and 15th amendments, including empowering the Justice Department to block discriminatory voting laws adopted in the states.

Federal oversight worked. As Michael Waldman of the Brennan Center for Justice testified on Wednesday: “The VRA is widely regarded as the single most effective piece of civil rights legislation in our nation’s history.” For example, in Mississippi in 1965, just 6 percent of eligible African Americans were registered to vote. By 1971, that number had grown to 60 percent. White voter registration increased, too.

In 2013, however, the Supreme Court returned immense power to the states when it eliminated the VRA’s requirement that jurisdictions with a history of unjust disenfranchisement must obtain Justice Department approval before changing their voting rules. After that decision, Shelby County v. Holder, state governments passed an onslaught of new voter regulations, most of them designed to reduce turnout among voters who leaned Democratic, including African Americans, Latinos and young people of all kinds.

Today’s growing disparities in access to the ballot clearly betray the promise of the Reconstruction amendments and their successors, including the 19th Amendment, which barred sex-based discrimination in voting. These amendments aimed to ensure that regardless of where you are in the country, you are entitled to certain rights including, for citizens, the right to vote, which is fundamental to democracy.

As long as voting rights are once again dramatically threatened in the states and Congress neglects to act — yet again thanks to the Senate filibuster — the most important action will take place at the state level.

In this context, we should look to Georgia not just for last week’s troubling new law, but also for the events that preceded it. Stacey Abrams and Lauren Groh-Wargo sounded a bit like 19th-century activists who helped prepare the ground for the Reconstruction amendments when they recently described some of “the unglamorous, tedious, sometimes technical, often contentious work” of building new political coalitions.

Their efforts helped Biden win Georgia. And by securing the election of two Democratic senators, they changed the balance of power in Washington and increased the odds that Congress might once again exercise its constitutional power to protect the rights of voters — which, as history shows, is the only sure way to safeguard American democracy.

This piece has been updated.