Before the shocking theft of the French Crown Jewels from the Louvre on October 19, most had all but forgotten the ruling women who once wore them during their 19th-century reigns. Even the Louvre’s own website offers little context—under “Object Location,” the page for each piece now reads the stinging phrase: “Not exhibited.” But the individual histories of the women who once owned these jeweled parures reveal much about France’s tumultuous political past—and bring those royal names to life.

Historian Raphaël Dargent, however, hasn’t forgotten them. He recently published biographies of Maria Amalia, the last queen of France, and of Empress Eugénie, both of whose jewels were stolen Sunday. Dargent told ARTnews that the theft of the eight jewels is especially painful given that they were among the few remaining Crown Jewels after most were auctioned off in 1887 by the French government, both to pay down debt and to rid the newly established Third Republic of monarchical symbols.

Two of the stolen pieces once belonged to Empress Eugénie: her pearl-and-diamond tiara and a bow-shaped brooch. Both were sold at that fateful 1887 auction and later repurchased for the Louvre more than a century later with the help of the Société des Amis du Louvr...