Noted female architect who designed the Hill-Stead Museum, Westover School and Avon Old Farms School.

Theodate was a strong-willed young woman who refused to answer to her given name, Effie, and wanted to be an architect, not a debutante. After continuing her studies at Miss Porter's School, Theodate spent a year touring Europe and then returned to Farmington, where she restored an eighteenth century cottage and attached a small house to it. She later designed a retirement home for her parents, now known as the Hill-Stead Museum; the firm of McKim, Mead and White prepared working drawings from her designs, effectively providing her with an apprenticeship in architecture.

A practicing architect for the next 30 years, Theodate's projects included designing adequate housing for her own employees, several country estates, and the reconstruction of Theodore Roosevelt's birthplace in Manhattan. From 1906-1909 she worked on one of her most extensive projects, the Westover School in Middlebury, the architectural design of which continues to receive high praise. In 1916, she designed the Hop Brook School in Naugatuck, and in 1920 she bought the land on which she would build Avon Old Farms School, the project which occupied the rest of her professional life.Theodate's unusual design for Avon was intended to reflect a progressive and highly individualistic philosophy of education.

Theodate was a major figure in the American Society for Psychical Research, along with her friend William James. She also survived the sinking of the Lusitania. At the age of 49, Theodate married John Riddle, a 52 year old diplomat who had served in Russia. She traveled to Argentina with him when he was appointed ambassador. In 1981, Theodate Pope Riddle was elected to the American Institute of Architects