Knauss became the last living American born during the presidency of Rutherford B. Hayes after the death of Wilhelmina Kott on 6 September 1994.
Her longevity first came to light after the death of Jeanne Calment in 1997. When Knauss and Marie-Louise Meilleur were first authenticated, it was believed that Mary Bidwell (19 May 1881 – 25 April 1996) was the oldest American.
Knauss was the seventh validated person to reach the age of 115, the fourth to reach 116, the third to reach 117, and the second to reach 118 and 119. She is also the third-oldest validated person ever, after Jeanne Calment of France and Kane Tanaka of Japan.
Until December 2020, Knauss was thought to have been one of only two validated American supercentenarians to have reached the age of 117 until Lucy Hannah’s age would end up being debunked, meaning that Knauss was the only validated supercentenarian in the history of the United States to reach the age of 117.
Knauss was the oldest validated person ever to achieve the title of world’s oldest living person, having achieved the title at the age of 117 years, 204 days on 16 April 1998, following the death of 117-year-old Marie-Louise Meilleur, until Lucile Randon achieved the title at the age of 118 years, 67 days on 19 April 2022, following the death of 119-year-old Kane Tanaka.
Knauss remains the only person from the United States to reach the ages of 117, 118, and 119, one of only two people from North America to reach the age of 117 (the other being Marie-Louise Meilleur), one of only four people to reach the age of 118 (the others being Jeanne Calment, Kane Tanaka, and Lucile Randon), and one of only three people to reach the age of 119 (the others being Jeanne Calment and Kane Tanaka).