Though the Civil War was over 150 years ago, the social fabric of the United States still suffers from the country's former divisions. Cultural and political values are split between the so-called free counties and the former slave counties, which existed in 15 states (only 11 of which seceded during the Civil War). Now, a new study has shown one of the most peculiar, yet perhaps unsurprising, divisions between former slaveholding and free parts of the U.S.: the prevalence of slavery in a given county correlates closely to the prevalence of firearms owned by its residents.

The researchers, led by psychology professor Dr. Nicholas Buttrick of the University of Wisconsin-Madison, hypothesize that this correlation exists because of the Reconstruction period in American history, which occurred immediately after the Civil War — "a moment when a massive upsurge in the availability of firearms co-occurred with a worldview threat from the emancipation and the political empowerment of Black Southerners."

Certainly that would explain why the correlation between slave ownership in 1860 and firearm ownership exists today, even when weighed against variables like "contemporary crime rates, police spending, degree of racial segregation and inequality, socioeconomic conditions, and voting patterns in the 2016 Presidential election," as well as why the data is "partially mediated by the frequency of people in the county reporting that they generally do not feel safe."

Speaking to Salon at first by email, and then later over the phone, Buttrick explained why there are only some occasions where worrying about safety wound up corresponding to gun ownership.

"We think it's especially interesting that it's only in areas with historically-high rates of enslavement or areas that are socially-connected to the same where we find that higher rates of feeling unsafe predict higher rates of gun ownership," Buttrick said. "For the rest of the country, we find almost no relationship between safety and gun ownership. In other words, we think that protective gun ownership — the belief that guns are the sort of thing that keeps a person safe (and the dominant gun culture in America) — may have some of its roots in attitudes formed by the institution of chattel slavery and its dissolution after the Civil War."

Buttrick emphasized that the study only establishes correlation. In addition, while connections to historic slave culture influence modern gun culture, these connections are hardly the only influence — or even the primary one.

"Modern American gun culture is a cocktail of a bunch of different ingredients, and even in our best models, the amount of variance explained by the impact of patterns of slavery isn't very big," Buttrick pointed out. "It's about as big as the impact of people voting for Trump in that county. So it's not nothing, but there's a lot of variance that slavery doesn't have anything to do with."