Belle Gunness, a Norwegian immigrant to America, is thought to be a serial killer with at least 14 murders attributed to her, but possibly up to 40. She was in Chicago, Illinois and La Porte, Indiana during her "active" killing years between 1884 and 1908. It is thought that her killing spree came to an end with her untimely demise in a house fire, though many people believe that she actually faked her death and lived out the remainder of her life elsewhere under a different identity.
Sources for this episode:
Wikipedia - Selbu, Chicago, Belle Gunness, Quinine, La Porte, Indiana
Only In Your State - An Indiana Woman Named Belle Was America's First Female Serial Killer
Legends of America - "Hell's Belle" Gunness - Black Widow of the Midwest