In November 1980, the Guinness Book of Records recognized her as the oldest documented person in history. For many years, it was believed that she attained this title when she surpassed the final age of Delina Filkins (1815–1928) on November 25, 1980 (November 15, according to the GRG, as noted below), at the age of 113 years, 215 days. However, in October 2023, LongeviQuest validated the age of Eliza Underwood (1867–1981), who was determined not only to have been born earlier than Thomas but also to have outlived her. Underwood’s validation revealed that Thomas was never the oldest person ever, not even the oldest living person in the United States at the time of her passing. However, Thomas did hold the title of the second-oldest person ever until Augusta Holtz surpassed her final age in May 1985.
On 17 November 1980, at the age of 113 years, 207 days, she surpassed the final age of Mary Kelly (1851–1964), becoming the oldest person to ever live in the U.S. state of California, as well as the third-oldest person ever, behind Underwood (who was still living at the time), and Delina Filkins. On 25 November, she surpassed Filkins’ final age, becoming the second-oldest person ever. She held the title of California’s longevity record holder until 7 April 1996, when her final age was surpassed by Miriam Carpelan.
Revalidation
Her age was recognized by the Guinness Book of Records during her life, and the validation was later recognized by the Gerontology Research Group. However, the GRG validated her date of birth as 14 April 1867, contrary to the claimed date of birth of 24 April 1867. In November 2023, following a thorough review of documentation uncovered by Jimmy Lindberg, the Global Validation Commission reached the conclusion that Thomas’ claimed date of birth was accurate.