After traveling abroad in Europe, Warren started library school at the University of Wisconsin, graduating in 1911.

In 1933 she became LAPL head librarian, one of six women overseeing large public libraries in the United States at that time.

She worked on the national level to increase federal aid to libraries and to end discrimination faced by African American librarians at ALA conference hotels.

[1] Warren retired in 1947 and then taught in library science programs in Wisconsin and Michigan and at the University of Southern California.

[1] Warren had a romantic relationship with Gladys English, the Los Angeles Public Library's head of the Children's Department.