Her father was an attorney and a Cook County judge, and her family was part of the city's upper class.

[1] Barnum's experience as a social worker led her to join the labor movement, as she felt that it was the best path to improve the lives of those who depended on the settlement houses.

In particular, she feuded with Leonora O'Reilly, an early member of the WTUL who resigned in 1905 due to her dissatisfaction with upper-class allies within the organization.

[3] After O'Reilly's resignation, Barnum rebuked her for leaving an organization which she felt was continuing to do good work despite her criticisms.

O'Reilly also criticized a book on the working class which Barnum had praised, claiming that it was an inaccurate depiction of the actual lives of working-class women.