Her father, George Guerrier, was an English immigrant who served in the American Civil War as a Second Lieutenant of Colored Infantry.

Guerrier spent a great deal of her childhood separated from her father and his side of the family due to his difficulty finding steady work.

She lived at times with her late mother's siblings, Anna and Walton Ricketson and her elderly Uncle Fox on her father's side.

"[2] The Ricketsons were friends with individuals such as Henry David Thoreau, Ralph Waldo Emerson, and the family of Amos Broson Alcott, which affected Guerrier's worldview.

The North Bennett Street services "underwent enormous shifts" similar to other changes seen in social welfare programs during the Progressive Era.

[2] It was originally meant to train "widows and the wives of incapacitated husbands" in vocational aspects, but by the 1890s when Guerrier joined the nursery, its programming was evolving to reflect principles of the Settlement House movement.

[2] Guerrier became the custodian for the North Bennett Street delivery station of the Boston Public Library and also became the coordinator of its reading room.

"[2] The group was made up of "daughters of Jewish, Eastern European, and southern Italian immigrants," which typically did not mix in the community as "invisible boundaries existed" based on language, religion, creed, and nationality.

In 1917, Guerrier took a six-month paid leave from her position at the library to volunteer her time in Washington D.C. for Herbert Hoover's National Food Administration.

The trip started in D.C. and sent Guerrier to cities such as Columbus, Ohio; Denver, Colorado; Los Angeles, California and Missoula, Montana.

She believed the libraries of the time did a great deal of work that was underappreciated, and she thought they lacked sufficient government funding.

Over the course of those years, Guerrier spent time compiling a book titled The Federal Executive Departments as Sources of Information for Libraries.

[4] Upon the completion of her book in 1919, Guerrier returned to work at the Boston Public Library as the "Supervisor of Circulation,"[1] because her old position had long ago been filled.

[1] Also during this time, she penned another book, titled We Pledged Allegiance, a Librarian's Intimate Story of the United States Food Administration.