Fredericka "Marm" Mandelbaum

(1818 – February 1894) was a New York entrepreneur and operated as a criminal fence to many of the street gangs and criminals of the city's underworld, handling between $1-5 million in stolen goods between 1862 until 1884. Like her principal rival John D. Grady and the Grady Gang, she also became a patron to the criminal elements of the city and was involved in financing and organizing numerous burglaries and other criminal operations throughout the post-American Civil War era.

Emigrating from Prussia with her husband Wolfe Mandelbaum, the two arrived in New York in 1848. Purchasing a dry goods store on Clinton Street, by 1854, the business was operating as a front for the Mandelbaums' criminal operations (she would later need to store goods in two large warehouses in the city). However, instead of waiting to be approached by criminals, Mandelbaum began financing thieves and burglars and was involved in planning some of the biggest thefts in the city's history. Expanding her operations, she controlled several gangs of blackmailers and confidence men as well as a school to recruit and teach younger criminals on pickpocketing. She was also a top competitor to the Grady Gang.