Democratic candidates are finally talking about domestic terrorism. Here’s why that matters.

Earlier this month, Democratic presidential candidate Beto O’ Rourke visited Oklahoma, making stops in Tulsa and Oklahoma City. O’Rourke, who has spent much of the month focused on the white supremacist shooting in his hometown of El Paso, highlighted the common historical thread that connects the two Oklahoma towns: their shared history of racial terrorism. He noted that the Oklahoma City bombing in 1995 flowed from the same vein of domestic terrorism and white nationalism as the violence perpetrated against African Americans in Tulsa’s Greenwood District in 1921.

During his tour of the Greenwood District, O’Rourke referred to the 1921 eventin Tulsa as “one of the largest acts of white-nationalist terror” and lauded the black entrepreneurs who skillfully built businesses that made up Tulsa’s “black Wall Street” and resiliently rebuilt after the massacre.

Ten years ago, and even during the last presidential election campaign, O’Rourke’s categorization of racialized violence as “white-nationalist terror” would have been unthinkable. And his description of the Tulsa massacre as something other than a “riot” would have probably been dismissed by many as “politically correct.” But this is no longer the case, and it shows how much Democratic candidates, in an effort to reach the party’s diverse and progressive base, have become far more historically literate than their predecessors.

Large numbers of African Americans first came to the Greenwood District in an effort to escape racial violence. After the Civil War, from the 1870s to the 1890s, the region that would become the state of Oklahoma (then known as Indian Territory and Oklahoma Territory) saw an influx of over 70,000 African Americans, fleeing lynchings, poverty and political coercion. The Greenwood District, built on land taken from Native Americans by the U.S. government, represented their new beginnings, their hard-fought social independence and the peak of their economic fortunes.