Youngest of the dozen children to Hyman and Rebecca Barnett Polock,Isabella spent her life in Philadelphia. Her Dutch-born parents hadsettled in the city by 1813, and there her father worked as a jewelerand devoted himself to Jewish communal life and charity. The familywere members of Congregation Mikveh Israel.

In 1857, at ceremony officiated by Rabbi IsaacLeeser, Isabella married MorrisRosenbach. Morris had immigrated from Gunzenhausen, Bavaraia,in 1844 and, like Abraham Simon Wolf—married to Rebecca’s sisterMiriam—he workedin the clothing trade, selling overalls and underwear. Morris andIsabella had eight children: the second-oldest, Philip,and the youngest, Abraham, learned from Isabella’s brother Mosesabout the world of rare books and would go on to become famousdealers and collectors.

Likeher parents, Isabella would be an active member of Mikveh Israel. Shesimilarly inherited her family’s commitment to charity, workingwith the Female Hebrew Benevolent Society and the Jewish Orphans’Society and raising money for the purchase and restoration of MountVernon.