[1] Bancroft was born in Denver, Colorado, on September 11, 1900,[3] to an established, "upper crust" family and was a third-generation Coloradan.

[1] Her parents were Ethel Force Norton, a socialite from Troy, New York,[4][5] and George Jarvis Bancroft,[6] a Coloradan who graduated in 1895 from Stanford University.

[9] George's wealth ebbed and flowed as he explored mining enterprises in Mexico and the western United States.

Ethel rented out the second floor of their home at 1081 Downing Street to help support her two daughters, Caroline and Peggy, who was born in 1905.

[3] Bancroft received her Bachelor of Arts from Smith College[7] and attended the University of Denver where she attained a master's degree in history.

[7] Standing six feet tall, she often wore paper flowers in braids that wound on the top of her head.

[3] In her will, Bancroft left her estate to the Colorado Historical Society and the Western History Department of the Denver Public Library,[2] which awards an annual literary prize in her name "to the author of the best book on Colorado or Western American History".

It is awarded to "an individual, organization or museum that has contributed to public awareness, interest or involvement in Colorado history, or to its advancement."