Mary Amelia Ingalls (January 10, 1865 – October 20, 1928) was born near the town of Pepin, Wisconsin. She was the first child of Caroline and Charles Ingalls. She was the older sister of author Laura Ingalls Wilder, who is best known for her Little House on the Prairie book series.
At the age of 14, Ingalls suffered an illness—thought to be scarlet fever—which caused her to lose her eyesight. A 2013 study published in the journal Pediatrics, concluded it was actually viral meningoencephalitis that caused Mary's blindness, based on evidence from first-hand accounts and newspaper reports of Mary's illness as well as relevant school registries and epidemiologic data on blindness and infectious diseases. Between 1881 and 1889, Mary attended the Iowa Braille and Sight Saving School in Vinton, Iowa.
The historical record is silent as to why Mary did not attend school during one year in that period, but she did finish the seven-year course of study in 1889 and graduated. She then returned home to De Smet, South Dakota and lived with her parents until their deaths. Mary contributed to the family income by making fly nets for horses. Later, she lived with her sister, Grace, and then her other sister, Carrie. She never married. She died on October 20, 1928 at the age of 63, as a result of pneumonia and complications from a stroke. She is buried at De Smet Cemetery.