This painting by French artist Étienne Jeaurat (1699–1789) from 1757 shows the conveyance of prostitutes to the Hôpital de la Salpêtrière in Paris. The Salpêtrière was built at the behest of Louis XIV (1638–1715) on the site of a former factory for munitions powder (saltpeter) and was established from 1656 as a hospital for women and the mentally ill. The aim of the institution was to take in the poor and beggars and thus keep them out of the city. Prostitutes were imprisoned and later forcibly shipped to the colonies.
La Conduite des filles de joie à la Salpêtrière : le passage près de la porte Saint-Bernard, oil on canvas, 65 x 82 cm, 1757, artist: Étienne Jeaurat (1699–1789); source: Musée Carnavalet, Histoire de Paris, http://www.parismuseescollections.paris.fr/fr/musee-carnavalet/oeuvres/la-conduite-des-filles-de-joie-a-la-salpetriere-le-passage-pres-de-la-porte#infos-principales, public domain.