Helen Parker was 38 at the end of the Civil War when she and Henry moved to Iowa. She was apparently suffering from some chronic disease or condition at that time. Josiah Grinnell remembered her in his autobiography:
“Prof. Parker wedded Miss Helen Fitch, a gifted authoress and the belle of Auburn, tenderly remembered as long a sufferer from a frightful casualty.”
I don’t know what the “frightful casualty” was, but she was probably in declining health throughout her stay in Iowa. Her health may have been a factor in their decision to move back east. The Parkers moved to Auburn, Massachusetts in the fall of 1870 and Helen died in December 4, 1874.
Henry A. Nelson in “The Auburn Seminary Record,” Vol. 2, Number 10, 1906 (digitized by Google) recalls a visit he had with the Rev. Henry W. Parker: