An Epidemiological Barrier
The Great Plague of Marseille began with a single ship. On May 25, 1720, the merchant vessel Grand-Saint-Antoine arrived in Marseille's harbor from the Levant. Although the ship had experienced several deaths at sea, its valuable cargo of silk and cotton bales was eagerly awaited for an annual trade fair. The ship's owner, who was also the deputy mayor of Marseille, successfully pressured health officials to lift the quarantine prematurely. This decision allowed rats carrying fleas infected with the bacterium Yersinia pestis to come ashore.
Within days, the disease began to spread through the city. Hospitals were quickly overwhelmed, and at the outbreak's peak, nearly 1,000 people died per day. The city's public health systems collapsed, leaving thousands of bodies in the streets. To stop the plague from consuming the rest of France, the Parliament of Aix passed an act imposing the death penalty for anyone communicating between Marseille and the rest of Provence. To enforce this cordon sanitaire, authorities ordered the construction of a physical barrier: the Mur de la Peste, or Plague Wall. The wall was intended to seal off the infected region and protect the neighboring papal territory of Comtat Venaissin.