Fanny and Lassor Agoos were married in Russia and had two young children when Lassor immigrated to Boston in the late 1870's. Soon after his arrival Lassor moved to Newburyport, where he worked as a peddler, and two years later sent for his wife and children. Lassor's family expanded to seven children. His business prospered, and he eventually established a kid leather company.

In 1919 the Lassor and Fanny Agoos Charitable Fund, Inc. was created with the initial sum of $100,000. Such generosity was unusual for this era, for by 1929 there were fewer than 200 similar foundations in the United States, and very few had been endowed by the grantor while alive, as the Agoos Fund had been. Lassor died in 1921 and Fanny in 1932.

Lassor Agoos and his wife Fanny were among the founders of Beth Israel Hospital, and Mr. Agoos served as vice president. Subsequent generations of the Agoos family have been active volunteers in the Beth Israel community. A gift from Fanny Agoos started the hospital's first multidisciplinary collection of medical volumes, and in 1966 the Lassor and Fanny Agoos Library was dedicated in the Rabb Building. Thanks to the continued generosity of the Agoos family the library has grown in size and technology, making the Agoos Library the cornerstone of the CareGroup library network.