In the decades after the Civil War, signs reading “Whites Only,” “No dogs, no Negros, no Mexicans,” and “Colored served in rear” delivered a humiliating message at the thresholds of countless Southern businesses, the Associated Press reported Tuesday. The signs spread across the region after Reconstruction and hardened into law under Jim Crow, a system that depended on the belief that Black people were inferior to white people in intellect, morality and behavior.

Reich, a historian and author of an encyclopedia on the Jim Crow era, told the AP that the signs were not merely cultural warnings but were backed by the threat of violence and the possibility of reenslavement through incarceration. After the Supreme Court’s 1896 Plessy ruling, they carried statutory power. “Allowing white and Black people to coexist as equals, the system’s supporters believed, might encourage interracial sexual relations and spur the rise of an abominable race,” Reich said. The fear of racial mixing, he noted, was a driving force behind the regime of separation.

The Civil Rights Act of 1964 ended legally sanctioned segregation, but the cultural and workforce divisions survived the removal of the signs, Reich argued. He said the Jim Crow system compelled white workers to identify more with their employers than with their Black co‑workers. “That continues to stifle opportunities for Black and white workers to organize and work together on common issues, including diversity and inclusion,” Reich told the AP. The result, he added, is a workforce that remains fractured along racial lines, weakening the bargaining power of wage earners and suppressing wages.

The signs and other Jim Crow relics are now housed in museums and historical collections, serving as teaching tools for a generation born decades after segregation became illegal. The AP feature, part of its “American Objects” series marking the nation’s 250th anniversary, examines how objects like segregation signage have shaped — and mis-shaped — American life.