When her father died in 1899, she enrolled at the library program at Pratt Institute at the advice of her friend Josephine Rathbone, who was then a faculty member there.

[2] By 1902, Isom had taken over as the head librarian of the association and was overseeing its transformation from a subscription-based private library to a tax-funded public institution for all of Portland.

This was in part due to Isom's lobbying of the Legislature to expand the law, as she did not feel that only city residents should be able to access libraries.

However, a county commissioner rallied an attack against one of her librarians, M. Louise Hunt, for refusing to buy Liberty Bonds as it conflicted with her pacifist beliefs.

[6] A bronze tablet with her likeness is displayed in the stairway at the Central Library, and the organization's administration building is named in her honor.