Disappeared. While in her care, 21 babies mysteriously vanished. During her time in Illinois, she provided housing for displaced children. No one ever found out what happened to those children; whether they were sold or murdered in her care is a mystery.
Forty. She may have killed over 40 people. When inspecting her farmhouse after the fire, men came forward voicing their suspicions about Gunness' behavior. This led to the search that uncovered various bodies buried throughout her property. "In all, there were around 40 people whose relatives claimed were missing and possibly murdered by Gunness, although there may have been upwards of 100 people associated with her who met odd, early deaths," Ranker reports.
Poison. She used poison to kill two of her own children and one of her husbands. Two of her children died as infants from what appeared to be arsenic poisoning symptoms. Both children had life insurance policies that she collected. Her first husband, Mad Sorenson, father of the children, died similarly.