Mary Sawtelle, one of the first women in Oregon to earn a medical degree, was born in New York in 1835, the daughter of Benjamin and Lucretia Avery. After the death of her father, a Methodist minister, her mother married John Stipp, a Primitive Baptist minister.

In 1848, the family traveled to Oregon Territory, where they settled on a claim in Marion County. In The Heroine of '49 (1891), a thinly veiled autobiography, Sawtelle wrote of life in Oregon, her medical studies, and her early efforts as a writer, speaker, and organizer for women's rights, including her special interest in women's property rights.

On October 7, 1849, at the age of fourteen, Mary Avery married Carsena A. Huntley. Twenty-one years Mary's senior, Huntley had returned from the California gold fields and consulted with Stipp about marrying his stepdaughter. Under the Donation Land Act of 1850, marriage would allow Huntley to file for another 320 acres under his wife's name. The Averys apparently gave Huntley their consent if Mary remained with them until she was seventeen and had no children until she was twenty-five. Before long, however, Huntley persuaded his new wife to live with him, and she bore her first child before she was fifteen years old.

Nine years later, while living in Douglas County, Mary Huntley grew increasingly frightened by her "violent and threatening" husband. She took their three children and filed for divorce in Roseburg. In November 1858, Judge Matthew P. Deady granted a divorce but awarded exclusive custody of the children to Huntley, who had falsely charged Mary with adultery. 

Denied access to her children, she moved to Salem and attended Willamette Institute, where she met Cheston M. Sawtelle, an opponent of organized religion. They married in December 1861, taught in various Oregon schools, and eventually had three children.

In the summer of 1869, Mary Sawtelle enrolled as Willamette's first woman medical student. She passed all of her courses except anatomy, her favorite subject, and decided not to retake the exam for fear of being failed again by the professor, Dr. Elmore Y. Chase.

Championed by women's rights friends such as Abigail Scott Duniway, editor of The New Northwest, Mary Sawtelle attended the New York Medical College and Hospital for Women; she graduated in 1872. The next year, while her husband completed his medical degree at Willamette, Sawtelle worked as a physician in Salem. The couple later practiced in Portland.

The Sawtelles moved to San Francisco in 1876. Cheston Sawtelle was admitted to the California Medical Association in 1879; Mary Sawtelle, a graduate of a homeopathic medical school, was not accepted until the following year. She helped form the Woman Suffrage Association of California in 1879 and organized the Women's Medical College of the Pacific Coast in 1881. In her Medico-Literary Journal (1878-1885), she gave women health advice, claimed that Chinese women spread syphilis, and argued for eugenic measures to prevent the diseased from reproducing.

Dr. Mary P. Sawtelle divorced Cheston Sawtelle in 1883 for failure to provide and was living in Los Angeles by 1888. In April 1894, she died at age fifty-nine in New York City.