Grandma Sarah Sprague - William's widow - Emily Sprague Riley's & Sarah Sprague Ball mother
Easily found US Census records min Marion Co., Ohio for this woman based on the information in the inscription on the back.
The records indicate that this Sarah Sprague was born about 1808, was once the wife of a William Sprague, but was widowed before 1850, lived independently for decades and worked as a "farm manager," raised at least three children alone after the death of her husband, and lived into her 70s. In 1870 the daughter Emily referenced in the inscription was a young adult still living at home with her mother.
1870 Census - Ohio, Marion Co., Montgomery Twp. - La Rue PO: Sarah Sprague, age 63, born in OH; with daughter Emily, age 24; and Sarah Ball, age 32 (relationship unspecified, but apparently another of Sarah Sprague's daughters ); with Ann Ball, age 7 (apparently Sarah Sprague Ball's daughter and Sarah Sprague's granddaughter). Searching back, we found an 1860 Census record for this woman as head of a family with Emily and a younger brother William H. Sarah was employed as a "farm manager." In the 1850 Census she was also head of her household, with Emily and William and an older daughter Sarah E. (clearly the Sarah Ball in the 1870 Census). Searching forward again, as of the 1880 Census, Sarah and daughter Emily were living along together - Sarah was 72 and Emily was 35. A family tree on ancestry.com indicated that her husband was William Sprague, that he died in 1850, and that by then the couple had had several children, some of whom apparently did not survive childhood, judging by the evidence in the Census and the information in that family tree.