Keller was born as Mary Alice Gipe in Altoona, Pennsylvania on 19 March 1876. She was the fourth of six children born to Isaac and Mary (née Honodel) Gipe. During her adult life, she went by her middle name.
At the age of 17, on 24 April 1893, Keller married her husband, German-born Louis Charles Keller, in Camden, New Jersey. They moved back to Altoona, and she gave birth to her only daughter, Edna, on 3 June the following year. In 1897, after saving for four years, the couple bought a hotel and ran it themselves; they bought another hotel in 1902.
The couple separated in 1914 while suffering marital problems and later divorced. They were, however, back together by 1930 and living in Altoona. Louis Keller died in 1943 aged 70. Keller then lived alone until 1963, when she moved in with her daughter in nearby Hollidaysburg.
As a centenarian, Keller was a regular churchgoer. She enjoyed sewing and tending a small flower garden. By her 105th birthday, she could no longer walk unaided, but she was still mentally sharp. After her daughter’s death in 1980, her granddaughter Mary took care of her; she moved to a Hollidaysburg nursing home before 1984.
Keller died at 7:15 a.m. on 19 March 1986, her 110th birthday. She was survived by two grandchildren, eight great-grandchildren, and 14 great-great-grandchildren.
Keller was first recognised for her longevity in the Altoona Mirror on the occasion of her 100th birthday in 1976, and was noted several times afterward. Her age was verified by the Kestenbaum Study and the SSA Study, and validated by the GRG on 12 July 2002.