In 1888, a young teacher from Maine, newly widowed and accompanied by her young daughter and niece, traveled across the country to relocate to California and start a new life. Within two months of her arrival in Los Angeles, Mary Caswell founded what would soon become Marlborough School, now the oldest independent girls' school in Southern California.
Over the century that followed, the school has grown and changed in many important ways. Today's student body is representative of the talent and diversity of greater Los Angeles, academic and athletic programs have expanded, college matriculation is highly competitive and distinguished, and campus facilities have kept pace with the educational innovation taking place inside the classroom.
- 1889 – Marlborough School, originally called St. Margaret's School for Girls, is founded by Mary Caswell.
- 1890 – Marlborough moves to a new location at the corner of 23rd and Scarff Streets.
- 1924 – Miss Ada Blake becomes the second Principal of Marlborough School.
- 1942 – Miss Ada Blake is succeeded as Principal by Georgia Caswell Overton, daughter of Mary Caswell.
- 1948 – Mrs. Helen Mitchell becomes Principal, focuses on preparing Marlborough graduates for college.
- 1958 – Helen and Kenneth Mitchell purchase Marlborough School.
- 1962 - Marlborough ushers in a new era as a non-profit foundation with its own Board of Trustees.
- 1968 – The “new” School is completed, and two years later, Robert Chumbook (1970-1990) becomes Headmaster.
- 1989 - Barbara Wagner joins Marlborough School.
- 2014 – Marlborough Celebrates 125 Years.
- 2015 – The Arden Project breaks ground as the final phase of a campus expansion envisioned in the 1960s.
- 2015 – Dr. Priscilla G. Sands becomes Head of School.
- 2022 – Jennifer Ciccarelli appointed as Head of School.