In July 1863, a riverboat bearing important cargo sailed into Louisville on the Ohio River. It was a shipment from the Union Army—not unusual in the days of the army’s occupation of the Kentucky city during the Civil War. But the Idahoe’s cargo was anything but ordinary, and the city refused to let the ship dock on its shores. 

The ship wasn’t carrying weaponry—its cargo was human. Inside were over 100 prostitutes from Nashville, women who had been forced onto the ship at the behest of Union Army officials trying to stem a public health crisis of sexually transmitted diseases. They blamed the prostitutes for causing and spreading the diseases, which were nearly impossible to treat in a time before modern contraceptives or medical treatments, so they banished them from Nashville.

The women’s failed trip north on the Idahoe, a chartered boat known forever after as the “floating whorehouse,” was just the beginning of a strange period in the city’s history. When nobody would allow the ship to stop at their shores, Nashville officials had to devise another solution to their city’s crisis. In response, the city legalized prostitution in an attempt to prevent women with sexually transmitted infections from passing them along to large number of soldiers.

Modern research has shown that when sex work is legalized, sexually transmitted diseases fall—but over a century ago, the potential benefits of regulated sex work seemed clear even without those studies. The brief but successful experiment only lasted through the end of the Civil War. But it proved the benefits of allowing sex workers to practice their trade publicly.