It is important to remember that the hangings, burnings and dismemberments of black American men, women and children that were relatively common in this country between the Civil War and World War II were often public events. They were sometimes advertised in newspapers and drew hundreds and even thousands of white spectators, including elected officials and leading citizens who were so swept up in the carnivals of death that they posed with their children for keepsake photographs within arm’s length of mutilated black corpses.

These episodes of horrific, communitywide violence have been erased from civic memory in lynching-belt states like Louisiana, Georgia, Alabama, Florida and Mississippi. But that will change if Bryan Stevenson, a civil rights attorney, succeeds in his mission to build markers and memorials at lynching sites throughout the South as a way of forcing communities and the country to confront an era of racial terror directly and recognize the role that it played in shaping the current racial landscape.

Mr. Stevenson’s organization, the Equal Justice Initiative, took a step in that direction on Tuesday when it released a report that chronicles nearly 4,000 lynchings of black people in 12 Southern states from 1877 to 1950. The report focuses on what it describes as “racial terror lynchings,” which were used to enforce Jim Crow laws and racial segregation. Victims in these cases were often murdered without being accused of actual crimes but for minor social transgressions that included talking back to whites or insisting on fairness and basic rights.

The report is the result of five years of hard work. Researchers reviewed local newspapers, historical archives and court records; interviewed local historians, survivors and victims’ descendants; and scrutinized contemporaneously published articles in African-American newspapers, which took a closer interest in these matters than the white press. In the end, researchers found at least 700 more lynchings in the 12 states than were previously reported, suggesting that “racial terror lynching” was far more common than was generally believed.