The Civil War may have freed an estimated 4 million slaves, but that wasn’t nearly the end of acts of racial violence committed against African Americans. Acts of domestic terrorism against black people include the thousands murdered in public lynchings. Now, an interactive map provides a detailed look at almost every documented lynching between the 1830s and 1960s.

The map is part of a website created by a group called Monroe Work Today, which takes its name from an early 20th century sociologist named Monroe Nathan Work, who spent decades compiling data and statistics on lynchings. While working at Alabama’s Tuskegee Institute, Work founded the school’s Department of Records and Research—the archives of which form the bones of the map’s information, Laura Bliss reports for CityLab.

By scrolling around a slider included on the map, users can see the earliest-known lynchings in the U.S. across the country. The data points can be viewed by year as well as by the victim’s ethnicity, allowing users to approach the sobering subject from a variety of perspectives.

The website also explains how lynching as term evolved in meaning throughout different regions and time periods. As the creators write on the website:

"There is no single way to describe all lynchings. Often a mob in western states (like California) staged a mock trial at the gallows, in order to pronounce the person ‘guilty’ before hanging. The spectacles of public mutilation happened most often in the South, but sometimes in West Virginia, Delaware and Maryland too. People in Northern states perpetrated lynchings as well: sometimes as a brutal execution, and sometimes more swiftly. Finally, the accusations levelled against Mexican- or dark skinned Sicilian-Americans to justify their murder were typically different than the charges made against black Americans."

It’s unlikely historians will ever know just how many lynchings happened throughout the history of the U.S., as many likely went unreported, or were not classified as lynchings in documentation at the time. However, the sheer number of those that are on the books is staggering—according to the Equal Justice Initiative’s (EJI) 2015 report, Lynching in America, more than 4,000 black people were publicly murdered in the U.S. between 1877 and 1950. Tools like this site serves as an important endeavor to help mark these dark parts of American history and make it more visible and accessible for all.