From the founding of the United States until long after the Civil War, hundreds of the elected leaders writing the nation’s laws were current or former slaveowners.

More than 1,700 people who served in the U.S. Congress in the 18th, 19th and even 20th centuries owned human beings at some point in their lives, according to a Washington Post investigation of censuses and other historical records.

The country is still grappling with the legacy of their embrace of slavery. The link between race and political power in early America echoes in complicated ways, from the racial inequities that persist to this day to the polarizing fights over voting rights and the way history is taught in schools.

The Washington Post created a database that shows enslavers in Congress represented 37 states, including not just the South but every state in New England, much of the Midwest, and many Western states.

Some were owners of enormous plantations, like Sen. Edward Lloyd V of Maryland, who enslaved 468 people in 1832 on the same estate where abolitionist Frederick Douglass was enslaved as a child. Many exerted great influence on the issue of slavery, like Sen. Elias Kent Kane, who enslaved five people in Illinois in 1820, and tried to formally legalize slavery in the state.

William Richardson, for example, a Democrat who fought for the Confederacy, died in office in 1914 after representing Alabama for 14 years. Another Democrat, Rebecca Latimer Felton, a suffragist and a white supremacist, was appointed to fill a Senate vacancy in 1922 and briefly represented Georgia at age 87. The first woman ever to serve in the Senate was a former slaveholder.

Enslavers came from all parts of the political spectrum. The Post’s database includes lawmakers who were members of more than 60 political parties. Federalists, Whigs, Unionists, Populists, Progressives, Prohibitionists and dozens more: All those parties included slaveholders.

The most common political affiliation among enslavers was the Democratic Party — 606 Democrats in Congress were slaveholders.

While the early Republican Party is associated with abolition, The Post found 481 slaveowners who identified as Republicans at some point in their elected careers.

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Historian Loren Schweninger, who spent years driving to more than 200 courthouses across the South to collect records on slavery, notes the importance of lawmakers’ personal stake in slavery as they passed laws codifying the practice. “They were protective of the institution, that’s for sure,” Schweninger said of state and federal lawmakers’ relationship with slavery. “There was brutality and there was all kinds of exploitation of slaves — but still there were laws.”