[1] Turnbull was the youngest of two daughters born to Alexander Halliday Sligh, an immigrant from Scotland, and Lucinda Hannah McConnell, whose family was among early Scotch-Irish settlers in Westmoreland County, Pennsylvania.
Turnbull attended the village school, a boarding school called Washington Female Seminary in 'Little Washington', then enrolled at Indiana State Teachers College (now Indiana University of Pennsylvania or IUP).
She also attended the University of Chicago before starting her career as a high school English teacher.
[3][6] These early novels have been identifies as offering subtle critiques of religious legalism, patriarchy, and industrial excesses.
[3] Over the span of her six-decade writing career, Turnbull's later works were increasingly regarded as having old-fashioned morality, which she and others attributed it to a hopeful outlook on life.