Annie Monahan was arguably the most successful "black widow" of the early twentieth century when you factor in the time it took for authorities to finally catch up with her. She had killed three husbands and her own niece, garnering sizable payouts from life insurance companies as she acted as a beneficiary in all of the cases. She performed these acts of murder in the sleepy town of New Haven, Connecticut, dealing with police who always seem to be one step behind her.
Monahan grew bolder with each murder, increasing payout amounts in each case and even marrying the younger brother of a man she had killed.