Janette Oke 
Love Comes Softly (Love Comes Softly Book #1) 

Love Comes Softly introduced the characters of Marty and Clark Davis, whose tragic circumstances brought them to a "marriage of convenience" on the frontier prairies during the mid 1800s. The story of how Clark’s patient, caring love mirrored that of the heavenly Father, drawing Marty to faith and to love, has captured the hearts and imaginations of over one million readers on Book One alone!